move browser to webbrowser/

15 files changed, 6699 insertions, 0 deletions

diff --git a/webbrowser/components/sessionstore/DocumentUtils.jsm b/webbrowser/components/sessionstore/DocumentUtils.jsm
new file mode 100644
index 0000000..6b3f729
--- /dev/null
+++ b/webbrowser/components/sessionstore/DocumentUtils.jsm
@@ -0,0 +1,230 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+this.EXPORTED_SYMBOLS = [ "DocumentUtils" ];
+
+const Cu = Components.utils;
+const Ci = Components.interfaces;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource:///modules/sessionstore/XPathGenerator.jsm");
+
+this.DocumentUtils = {
+  /**
+   * Obtain form data for a DOMDocument instance.
+   *
+   * The returned object has 2 keys, "id" and "xpath". Each key holds an object
+   * which further defines form data.
+   *
+   * The "id" object maps element IDs to values. The "xpath" object maps the
+   * XPath of an element to its value.
+   *
+   * @param  aDocument
+   *         DOMDocument instance to obtain form data for.
+   * @return object
+   *         Form data encoded in an object.
+   */
+  getFormData: function DocumentUtils_getFormData(aDocument) {
+    let formNodes = aDocument.evaluate(
+      XPathGenerator.restorableFormNodes,
+      aDocument,
+      XPathGenerator.resolveNS,
+      Ci.nsIDOMXPathResult.UNORDERED_NODE_ITERATOR_TYPE, null
+    );
+
+    let node;
+    let ret = {id: {}, xpath: {}};
+
+    // Limit the number of XPath expressions for performance reasons. See
+    // bug 477564.
+    const MAX_TRAVERSED_XPATHS = 100;
+    let generatedCount = 0;
+
+    while (node = formNodes.iterateNext()) {
+      let nId = node.id;
+      let hasDefaultValue = true;
+      let value;
+
+      // Only generate a limited number of XPath expressions for perf reasons
+      // (cf. bug 477564)
+      if (!nId && generatedCount > MAX_TRAVERSED_XPATHS) {
+        continue;
+      }
+
+      if (node instanceof Ci.nsIDOMHTMLInputElement ||
+          node instanceof Ci.nsIDOMHTMLTextAreaElement) {
+        switch (node.type) {
+          case "checkbox":
+          case "radio":
+            value = node.checked;
+            hasDefaultValue = value == node.defaultChecked;
+            break;
+          case "file":
+            value = { type: "file", fileList: node.mozGetFileNameArray() };
+            hasDefaultValue = !value.fileList.length;
+            break;
+          default: // text, textarea
+            value = node.value;
+            hasDefaultValue = value == node.defaultValue;
+            break;
+        }
+      } else if (!node.multiple) {
+        // <select>s without the multiple attribute are hard to determine the
+        // default value, so assume we don't have the default.
+        hasDefaultValue = false;
+        value = { selectedIndex: node.selectedIndex, value: node.value };
+      } else {
+        // <select>s with the multiple attribute are easier to determine the
+        // default value since each <option> has a defaultSelected
+        let options = Array.map(node.options, function(aOpt, aIx) {
+          let oSelected = aOpt.selected;
+          hasDefaultValue = hasDefaultValue && (oSelected == aOpt.defaultSelected);
+          return oSelected ? aOpt.value : -1;
+        });
+        value = options.filter(function(aIx) aIx !== -1);
+      }
+
+      // In order to reduce XPath generation (which is slow), we only save data
+      // for form fields that have been changed. (cf. bug 537289)
+      if (!hasDefaultValue) {
+        if (nId) {
+          ret.id[nId] = value;
+        } else {
+          generatedCount++;
+          ret.xpath[XPathGenerator.generate(node)] = value;
+        }
+      }
+    }
+
+    return ret;
+  },
+
+  /**
+   * Merges form data on a document from previously obtained data.
+   *
+   * This is the inverse of getFormData(). The data argument is the same object
+   * type which is returned by getFormData(): an object containing the keys
+   * "id" and "xpath" which are each objects mapping element identifiers to
+   * form values.
+   *
+   * Where the document has existing form data for an element, the value
+   * will be replaced. Where the document has a form element but no matching
+   * data in the passed object, the element is untouched.
+   *
+   * @param  aDocument
+   *         DOMDocument instance to which to restore form data.
+   * @param  aData
+   *         Object defining form data.
+   */
+  mergeFormData: function DocumentUtils_mergeFormData(aDocument, aData) {
+    if ("xpath" in aData) {
+      for each (let [xpath, value] in Iterator(aData.xpath)) {
+        let node = XPathGenerator.resolve(aDocument, xpath);
+
+        if (node) {
+          this.restoreFormValue(node, value, aDocument);
+        }
+      }
+    }
+
+    if ("id" in aData) {
+      for each (let [id, value] in Iterator(aData.id)) {
+        let node = aDocument.getElementById(id);
+
+        if (node) {
+          this.restoreFormValue(node, value, aDocument);
+        }
+      }
+    }
+  },
+
+  /**
+   * Low-level function to restore a form value to a DOMNode.
+   *
+   * If you want a higher-level interface, see mergeFormData().
+   *
+   * When the value is changed, the function will fire the appropriate DOM
+   * events.
+   *
+   * @param  aNode
+   *         DOMNode to set form value on.
+   * @param  aValue
+   *         Value to set form element to.
+   * @param  aDocument [optional]
+   *         DOMDocument node belongs to. If not defined, node.ownerDocument
+   *         is used.
+   */
+  restoreFormValue: function DocumentUtils_restoreFormValue(aNode, aValue, aDocument) {
+    aDocument = aDocument || aNode.ownerDocument;
+
+    let eventType;
+
+    if (typeof aValue == "string" && aNode.type != "file") {
+      // Don't dispatch an input event if there is no change.
+      if (aNode.value == aValue) {
+        return;
+      }
+
+      aNode.value = aValue;
+      eventType = "input";
+    } else if (typeof aValue == "boolean") {
+      // Don't dispatch a change event for no change.
+      if (aNode.checked == aValue) {
+        return;
+      }
+
+      aNode.checked = aValue;
+      eventType = "change";
+    } else if (typeof aValue == "number") {
+      // handle select backwards compatibility, example { "#id" : index }
+      // We saved the value blindly since selects take more work to determine
+      // default values. So now we should check to avoid unnecessary events.
+      if (aNode.selectedIndex == aValue) {
+        return;
+      }
+
+      if (aValue < aNode.options.length) {
+        aNode.selectedIndex = aValue;
+        eventType = "change";
+      }
+    } else if (aValue && aValue.selectedIndex >= 0 && aValue.value) {
+      // handle select new format
+
+      // Don't dispatch a change event for no change
+      if (aNode.options[aNode.selectedIndex].value == aValue.value) {
+        return;
+      }
+
+      // find first option with matching aValue if possible
+      for (let i = 0; i < aNode.options.length; i++) {
+        if (aNode.options[i].value == aValue.value) {
+          aNode.selectedIndex = i;
+          break;
+        }
+      }
+      eventType = "change";
+    } else if (aValue && aValue.fileList && aValue.type == "file" &&
+      aNode.type == "file") {
+      aNode.mozSetFileNameArray(aValue.fileList, aValue.fileList.length);
+      eventType = "input";
+    } else if (aValue && typeof aValue.indexOf == "function" && aNode.options) {
+      Array.forEach(aNode.options, function(opt, index) {
+        // don't worry about malformed options with same values
+        opt.selected = aValue.indexOf(opt.value) > -1;
+
+        // Only fire the event here if this wasn't selected by default
+        if (!opt.defaultSelected) {
+          eventType = "change";
+        }
+      });
+    }
+
+    // Fire events for this node if applicable
+    if (eventType) {
+      let event = aDocument.createEvent("UIEvents");
+      event.initUIEvent(eventType, true, true, aDocument.defaultView, 0);
+      aNode.dispatchEvent(event);
+    }
+  }
+};
diff --git a/webbrowser/components/sessionstore/SessionStorage.jsm b/webbrowser/components/sessionstore/SessionStorage.jsm
new file mode 100644
index 0000000..64aef35
--- /dev/null
+++ b/webbrowser/components/sessionstore/SessionStorage.jsm
@@ -0,0 +1,165 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+* License, v. 2.0. If a copy of the MPL was not distributed with this file,
+* You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+this.EXPORTED_SYMBOLS = ["SessionStorage"];
+
+const Cu = Components.utils;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "SessionStore",
+  "resource:///modules/sessionstore/SessionStore.jsm");
+
+this.SessionStorage = {
+  /**
+   * Updates all sessionStorage "super cookies"
+   * @param aDocShell
+   *        That tab's docshell (containing the sessionStorage)
+   * @param aFullData
+   *        always return privacy sensitive data (use with care)
+   */
+  serialize: function ssto_serialize(aDocShell, aFullData) {
+    return DomStorage.read(aDocShell, aFullData);
+  },
+
+  /**
+   * Restores all sessionStorage "super cookies".
+   * @param aDocShell
+   *        A tab's docshell (containing the sessionStorage)
+   * @param aStorageData
+   *        Storage data to be restored
+   */
+  deserialize: function ssto_deserialize(aDocShell, aStorageData) {
+    DomStorage.write(aDocShell, aStorageData);
+  }
+};
+
+Object.freeze(SessionStorage);
+
+var DomStorage = {
+  /**
+   * Reads all session storage data from the given docShell.
+   * @param aDocShell
+   *        A tab's docshell (containing the sessionStorage)
+   * @param aFullData
+   *        Always return privacy sensitive data (use with care)
+   */
+  read: function DomStorage_read(aDocShell, aFullData) {
+    let data = {};
+    let isPinned = aDocShell.isAppTab;
+    let shistory = aDocShell.sessionHistory;
+
+    for (let i = 0; i < shistory.count; i++) {
+      let principal = History.getPrincipalForEntry(shistory, i, aDocShell);
+      if (!principal)
+        continue;
+
+      // Check if we're allowed to store sessionStorage data.
+      let isHTTPS = principal.URI && principal.URI.schemeIs("https");
+      if (aFullData || SessionStore.checkPrivacyLevel(isHTTPS, isPinned)) {
+        let origin = principal.extendedOrigin;
+
+        // Don't read a host twice.
+        if (!(origin in data)) {
+          let originData = this._readEntry(principal, aDocShell);
+          if (Object.keys(originData).length) {
+            data[origin] = originData;
+          }
+        }
+      }
+    }
+
+    return data;
+  },
+
+  /**
+   * Writes session storage data to the given tab.
+   * @param aDocShell
+   *        A tab's docshell (containing the sessionStorage)
+   * @param aStorageData
+   *        Storage data to be restored
+   */
+  write: function DomStorage_write(aDocShell, aStorageData) {
+    for (let [host, data] in Iterator(aStorageData)) {
+      let uri = Services.io.newURI(host, null, null);
+      let principal = Services.scriptSecurityManager.getDocShellCodebasePrincipal(uri, aDocShell);
+      let storageManager = aDocShell.QueryInterface(Components.interfaces.nsIDOMStorageManager);
+      let window = aDocShell.QueryInterface(Components.interfaces.nsIInterfaceRequestor)
+                            .getInterface(Components.interfaces.nsIDOMWindow);
+
+      // There is no need to pass documentURI, it's only used to fill documentURI property of
+      // domstorage event, which in this case has no consumer.  Prevention of events in case
+      // of missing documentURI will be solved in a followup bug to bug 600307.
+      try {
+        let storage = storageManager.createStorage(window, principal, "", aDocShell.usePrivateBrowsing);
+      } catch(e) {
+        Cu.reportError(e);
+      }
+
+      for (let [key, value] in Iterator(data)) {
+        try {
+          storage.setItem(key, value);
+        } catch (e) {
+          // throws e.g. for URIs that can't have sessionStorage
+          Cu.reportError(e);
+        }
+      }
+    }
+  },
+
+  /**
+   * Reads an entry in the session storage data contained in a tab's history.
+   * @param aURI
+   *        That history entry uri
+   * @param aDocShell
+   *        A tab's docshell (containing the sessionStorage)
+   */
+  _readEntry: function DomStorage_readEntry(aPrincipal, aDocShell) {
+    let hostData = {};
+    let storage;
+
+    try {
+      let storageManager = aDocShell.QueryInterface(Components.interfaces.nsIDOMStorageManager);
+      storage = storageManager.getStorage(aPrincipal);
+    } catch (e) {
+      // sessionStorage might throw if it's turned off, see bug 458954
+    }
+
+    if (storage && storage.length) {
+       for (let i = 0; i < storage.length; i++) {
+        try {
+          let key = storage.key(i);
+          hostData[key] = storage.getItem(key);
+        } catch (e) {
+          // This currently throws for secured items (cf. bug 442048).
+        }
+      }
+    }
+
+    return hostData;
+  }
+};
+
+var History = {
+  /**
+   * Returns a given history entry's URI.
+   * @param aHistory
+   *        That tab's session history
+   * @param aIndex
+   *        The history entry's index
+   * @param aDocShell
+   *        That tab's docshell
+   */
+  getPrincipalForEntry: function History_getPrincipalForEntry(aHistory,
+                                                              aIndex,
+                                                              aDocShell) {
+    try {
+      return Services.scriptSecurityManager.getDocShellCodebasePrincipal(
+        aHistory.getEntryAtIndex(aIndex, false).URI, aDocShell);
+    } catch (e) {
+      // This might throw for some reason.
+    }
+  },
+};
diff --git a/webbrowser/components/sessionstore/SessionStore.jsm b/webbrowser/components/sessionstore/SessionStore.jsm
new file mode 100644
index 0000000..e19a578
--- /dev/null
+++ b/webbrowser/components/sessionstore/SessionStore.jsm
@@ -0,0 +1,4786 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+this.EXPORTED_SYMBOLS = ["SessionStore"];
+
+const Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+
+const STATE_STOPPED = 0;
+const STATE_RUNNING = 1;
+const STATE_QUITTING = -1;
+
+const STATE_STOPPED_STR = "stopped";
+const STATE_RUNNING_STR = "running";
+
+const TAB_STATE_NEEDS_RESTORE = 1;
+const TAB_STATE_RESTORING = 2;
+
+const PRIVACY_NONE = 0;
+const PRIVACY_ENCRYPTED = 1;
+const PRIVACY_FULL = 2;
+
+const NOTIFY_WINDOWS_RESTORED = "sessionstore-windows-restored";
+const NOTIFY_BROWSER_STATE_RESTORED = "sessionstore-browser-state-restored";
+
+// Default maximum number of tabs to restore simultaneously. Controlled by
+// the browser.sessionstore.max_concurrent_tabs pref.
+const DEFAULT_MAX_CONCURRENT_TAB_RESTORES = 3;
+
+// global notifications observed
+const OBSERVING = [
+  "domwindowopened", "domwindowclosed",
+  "quit-application-requested", "quit-application-granted",
+  "browser-lastwindow-close-granted",
+  "quit-application", "browser:purge-session-history",
+  "browser:purge-domain-data"
+];
+
+// XUL Window properties to (re)store
+// Restored in restoreDimensions()
+const WINDOW_ATTRIBUTES = ["width", "height", "screenX", "screenY", "sizemode"];
+
+// Hideable window features to (re)store
+// Restored in restoreWindowFeatures()
+const WINDOW_HIDEABLE_FEATURES = [
+  "menubar", "toolbar", "locationbar", "personalbar", "statusbar", "scrollbars"
+];
+
+const MESSAGES = [
+  // The content script tells us that its form data (or that of one of its
+  // subframes) might have changed. This can be the contents or values of
+  // standard form fields or of ContentEditables.
+  "SessionStore:input",
+
+  // The content script has received a pageshow event. This happens when a
+  // page is loaded from bfcache without any network activity, i.e. when
+  // clicking the back or forward button.
+  "SessionStore:pageshow"
+];
+
+// These are tab events that we listen to.
+const TAB_EVENTS = [
+  "TabOpen", "TabClose", "TabSelect", "TabShow", "TabHide", "TabPinned",
+  "TabUnpinned"
+];
+
+#ifndef XP_WIN
+#define BROKEN_WM_Z_ORDER
+#endif
+
+Cu.import("resource://gre/modules/Services.jsm", this);
+Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
+// debug.js adds NS_ASSERT. cf. bug 669196
+Cu.import("resource://gre/modules/debug.js", this);
+Cu.import("resource://gre/modules/osfile.jsm", this);
+Cu.import("resource://gre/modules/PrivateBrowsingUtils.jsm", this);
+Cu.import("resource://gre/modules/Promise.jsm", this);
+
+XPCOMUtils.defineLazyServiceGetter(this, "gSessionStartup",
+  "@mozilla.org/browser/sessionstartup;1", "nsISessionStartup");
+XPCOMUtils.defineLazyServiceGetter(this, "gScreenManager",
+  "@mozilla.org/gfx/screenmanager;1", "nsIScreenManager");
+
+// List of docShell capabilities to (re)store. These are automatically
+// retrieved from a given docShell if not already collected before.
+// This is made so they're automatically in sync with all nsIDocShell.allow*
+// properties.
+var gDocShellCapabilities = (function () {
+  let caps;
+
+  return docShell => {
+    if (!caps) {
+      let keys = Object.keys(docShell);
+      caps = keys.filter(k => k.startsWith("allow")).map(k => k.slice(5));
+    }
+
+    return caps;
+  };
+})();
+
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+  "resource://gre/modules/NetUtil.jsm");
+
+#ifdef MOZ_DEVTOOLS
+XPCOMUtils.defineLazyModuleGetter(this, "ScratchpadManager",
+  "resource://devtools/client/scratchpad/scratchpad-manager.jsm");
+
+Object.defineProperty(this, "HUDService", {
+  get: function HUDService_getter() {
+    let devtools = Cu.import("resource://devtools/shared/Loader.jsm", {}).devtools;
+    return devtools.require("devtools/client/webconsole/hudservice").HUDService;
+  },
+  configurable: true,
+  enumerable: true
+});
+#endif  
+  
+XPCOMUtils.defineLazyModuleGetter(this, "DocumentUtils",
+  "resource:///modules/sessionstore/DocumentUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "SessionStorage",
+  "resource:///modules/sessionstore/SessionStorage.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "_SessionFile",
+  "resource:///modules/sessionstore/_SessionFile.jsm");
+
+function debug(aMsg) {
+  aMsg = ("SessionStore: " + aMsg).replace(/\S{80}/g, "$&\n");
+  Services.console.logStringMessage(aMsg);
+}
+
+this.SessionStore = {
+  get promiseInitialized() {
+    return SessionStoreInternal.promiseInitialized.promise;
+  },
+
+  get canRestoreLastSession() {
+    return SessionStoreInternal.canRestoreLastSession;
+  },
+
+  set canRestoreLastSession(val) {
+    SessionStoreInternal.canRestoreLastSession = val;
+  },
+
+  init: function ss_init(aWindow) {
+    return SessionStoreInternal.init(aWindow);
+  },
+
+  getBrowserState: function ss_getBrowserState() {
+    return SessionStoreInternal.getBrowserState();
+  },
+
+  setBrowserState: function ss_setBrowserState(aState) {
+    SessionStoreInternal.setBrowserState(aState);
+  },
+
+  getWindowState: function ss_getWindowState(aWindow) {
+    return SessionStoreInternal.getWindowState(aWindow);
+  },
+
+  setWindowState: function ss_setWindowState(aWindow, aState, aOverwrite) {
+    SessionStoreInternal.setWindowState(aWindow, aState, aOverwrite);
+  },
+
+  getTabState: function ss_getTabState(aTab) {
+    return SessionStoreInternal.getTabState(aTab);
+  },
+
+  setTabState: function ss_setTabState(aTab, aState) {
+    SessionStoreInternal.setTabState(aTab, aState);
+  },
+
+  duplicateTab: function ss_duplicateTab(aWindow, aTab, aDelta) {
+    return SessionStoreInternal.duplicateTab(aWindow, aTab, aDelta);
+  },
+
+  getClosedTabCount: function ss_getClosedTabCount(aWindow) {
+    return SessionStoreInternal.getClosedTabCount(aWindow);
+  },
+
+  getClosedTabData: function ss_getClosedTabDataAt(aWindow) {
+    return SessionStoreInternal.getClosedTabData(aWindow);
+  },
+
+  undoCloseTab: function ss_undoCloseTab(aWindow, aIndex) {
+    return SessionStoreInternal.undoCloseTab(aWindow, aIndex);
+  },
+
+  forgetClosedTab: function ss_forgetClosedTab(aWindow, aIndex) {
+    return SessionStoreInternal.forgetClosedTab(aWindow, aIndex);
+  },
+
+  getClosedWindowCount: function ss_getClosedWindowCount() {
+    return SessionStoreInternal.getClosedWindowCount();
+  },
+
+  getClosedWindowData: function ss_getClosedWindowData() {
+    return SessionStoreInternal.getClosedWindowData();
+  },
+
+  undoCloseWindow: function ss_undoCloseWindow(aIndex) {
+    return SessionStoreInternal.undoCloseWindow(aIndex);
+  },
+
+  forgetClosedWindow: function ss_forgetClosedWindow(aIndex) {
+    return SessionStoreInternal.forgetClosedWindow(aIndex);
+  },
+
+  getWindowValue: function ss_getWindowValue(aWindow, aKey) {
+    return SessionStoreInternal.getWindowValue(aWindow, aKey);
+  },
+
+  setWindowValue: function ss_setWindowValue(aWindow, aKey, aStringValue) {
+    SessionStoreInternal.setWindowValue(aWindow, aKey, aStringValue);
+  },
+
+  deleteWindowValue: function ss_deleteWindowValue(aWindow, aKey) {
+    SessionStoreInternal.deleteWindowValue(aWindow, aKey);
+  },
+
+  getTabValue: function ss_getTabValue(aTab, aKey) {
+    return SessionStoreInternal.getTabValue(aTab, aKey);
+  },
+
+  setTabValue: function ss_setTabValue(aTab, aKey, aStringValue) {
+    SessionStoreInternal.setTabValue(aTab, aKey, aStringValue);
+  },
+
+  deleteTabValue: function ss_deleteTabValue(aTab, aKey) {
+    SessionStoreInternal.deleteTabValue(aTab, aKey);
+  },
+
+  persistTabAttribute: function ss_persistTabAttribute(aName) {
+    SessionStoreInternal.persistTabAttribute(aName);
+  },
+
+  restoreLastSession: function ss_restoreLastSession() {
+    SessionStoreInternal.restoreLastSession();
+  },
+
+  checkPrivacyLevel: function ss_checkPrivacyLevel(aIsHTTPS, aUseDefaultPref) {
+    return SessionStoreInternal.checkPrivacyLevel(aIsHTTPS, aUseDefaultPref);
+  }
+};
+
+// Freeze the SessionStore object. We don't want anyone to modify it.
+Object.freeze(SessionStore);
+
+var SessionStoreInternal = {
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsIDOMEventListener,
+    Ci.nsIObserver,
+    Ci.nsISupportsWeakReference
+  ]),
+
+  // set default load state
+  _loadState: STATE_STOPPED,
+
+  // During the initial restore and setBrowserState calls tracks the number of
+  // windows yet to be restored
+  _restoreCount: -1,
+
+  // whether a setBrowserState call is in progress
+  _browserSetState: false,
+
+  // time in milliseconds (Date.now()) when the session was last written to file
+  _lastSaveTime: 0,
+
+  // time in milliseconds when the session was started (saved across sessions),
+  // defaults to now if no session was restored or timestamp doesn't exist
+  _sessionStartTime: Date.now(),
+
+  // states for all currently opened windows
+  _windows: {},
+
+  // internal states for all open windows (data we need to associate,
+  // but not write to disk)
+  _internalWindows: {},
+
+  // states for all recently closed windows
+  _closedWindows: [],
+
+  // not-"dirty" windows usually don't need to have their data updated
+  _dirtyWindows: {},
+
+  // collection of session states yet to be restored
+  _statesToRestore: {},
+
+  // counts the number of crashes since the last clean start
+  _recentCrashes: 0,
+
+  // whether the last window was closed and should be restored
+  _restoreLastWindow: false,
+
+  // number of tabs currently restoring
+  _tabsRestoringCount: 0,
+  
+  // max number of tabs to restore concurrently
+  _maxConcurrentTabRestores: DEFAULT_MAX_CONCURRENT_TAB_RESTORES,
+  
+  // whether restored tabs load cached versions or force a reload
+  _cacheBehavior: 0,
+  
+  // The state from the previous session (after restoring pinned tabs). This
+  // state is persisted and passed through to the next session during an app
+  // restart to make the third party add-on warning not trash the deferred
+  // session
+  _lastSessionState: null,
+
+  // When starting Firefox with a single private window, this is the place
+  // where we keep the session we actually wanted to restore in case the user
+  // decides to later open a non-private window as well.
+  _deferredInitialState: null,
+
+  // A promise resolved once initialization is complete
+  _promiseInitialization: Promise.defer(),
+
+  // Whether session has been initialized
+  _sessionInitialized: false,
+
+  // True if session store is disabled by multi-process browsing.
+  // See bug 516755.
+  _disabledForMultiProcess: false,
+
+  // The original "sessionstore.resume_session_once" preference value before it
+  // was modified by saveState.  saveState will set the
+  // "sessionstore.resume_session_once" to true when the
+  // the "sessionstore.resume_from_crash" preference is false (crash recovery
+  // is disabled) so that pinned tabs will be restored in the case of a
+  // crash.  This variable is used to restore the original value so the
+  // previous session is not always restored when
+  // "sessionstore.resume_from_crash" is true.
+  _resume_session_once_on_shutdown: null,
+
+  /**
+   * A promise fulfilled once initialization is complete.
+   */
+  get promiseInitialized() {
+    return this._promiseInitialization;
+  },
+
+  /* ........ Public Getters .............. */
+  get canRestoreLastSession() {
+    return this._lastSessionState;
+  },
+
+  set canRestoreLastSession(val) {
+    this._lastSessionState = null;
+  },
+
+  /* ........ Global Event Handlers .............. */
+
+  /**
+   * Initialize the component
+   */
+  initService: function ssi_initService() {
+    if (this._sessionInitialized) {
+      return;
+    }
+    OBSERVING.forEach(function(aTopic) {
+      Services.obs.addObserver(this, aTopic, true);
+    }, this);
+
+    this._initPrefs();
+
+    this._disabledForMultiProcess = false;
+
+    // this pref is only read at startup, so no need to observe it
+    this._sessionhistory_max_entries =
+      this._prefBranch.getIntPref("sessionhistory.max_entries");
+
+    gSessionStartup.onceInitialized.then(
+      this.initSession.bind(this)
+    );
+  },
+
+  initSession: function ssi_initSession() {
+    let ss = gSessionStartup;
+    try {
+      if (ss.doRestore() ||
+          ss.sessionType == Ci.nsISessionStartup.DEFER_SESSION)
+        this._initialState = ss.state;
+    }
+    catch(ex) { dump(ex + "\n"); } // no state to restore, which is ok
+
+    if (this._initialState) {
+      try {
+        // If we're doing a DEFERRED session, then we want to pull pinned tabs
+        // out so they can be restored.
+        if (ss.sessionType == Ci.nsISessionStartup.DEFER_SESSION) {
+          let [iniState, remainingState] = this._prepDataForDeferredRestore(this._initialState);
+          // If we have a iniState with windows, that means that we have windows
+          // with app tabs to restore.
+          if (iniState.windows.length)
+            this._initialState = iniState;
+          else
+            this._initialState = null;
+          if (remainingState.windows.length)
+            this._lastSessionState = remainingState;
+        }
+        else {
+          // Get the last deferred session in case the user still wants to
+          // restore it
+          this._lastSessionState = this._initialState.lastSessionState;
+
+          let lastSessionCrashed =
+            this._initialState.session && this._initialState.session.state &&
+            this._initialState.session.state == STATE_RUNNING_STR;
+          if (lastSessionCrashed) {
+            this._recentCrashes = (this._initialState.session &&
+                                   this._initialState.session.recentCrashes || 0) + 1;
+
+            if (this._needsRestorePage(this._initialState, this._recentCrashes)) {
+              // replace the crashed session with a restore-page-only session
+              let pageData = {
+                url: "about:sessionrestore",
+                formdata: {
+                  id: { "sessionData": this._initialState },
+                  xpath: {}
+                }
+              };
+              this._initialState = { windows: [{ tabs: [{ entries: [pageData] }] }] };
+            }
+          }
+
+          // Load the session start time from the previous state
+          this._sessionStartTime = this._initialState.session &&
+                                   this._initialState.session.startTime ||
+                                   this._sessionStartTime;
+
+          // make sure that at least the first window doesn't have anything hidden
+          delete this._initialState.windows[0].hidden;
+          // Since nothing is hidden in the first window, it cannot be a popup
+          delete this._initialState.windows[0].isPopup;
+          // We don't want to minimize and then open a window at startup.
+          if (this._initialState.windows[0].sizemode == "minimized")
+            this._initialState.windows[0].sizemode = "normal";
+          // clear any lastSessionWindowID attributes since those don't matter
+          // during normal restore
+          this._initialState.windows.forEach(function(aWindow) {
+            delete aWindow.__lastSessionWindowID;
+          });
+        }
+      }
+      catch (ex) { debug("The session file is invalid: " + ex); }
+    }
+
+    // A Lazy getter for the sessionstore.js backup promise.
+    XPCOMUtils.defineLazyGetter(this, "_backupSessionFileOnce", function () {
+      return _SessionFile.createBackupCopy();
+    });
+
+    // at this point, we've as good as resumed the session, so we can
+    // clear the resume_session_once flag, if it's set
+    if (this._loadState != STATE_QUITTING &&
+        this._prefBranch.getBoolPref("sessionstore.resume_session_once"))
+      this._prefBranch.setBoolPref("sessionstore.resume_session_once", false);
+
+    this._initEncoding();
+
+    // Session is ready.
+    this._sessionInitialized = true;
+    this._promiseInitialization.resolve();
+  },
+
+  _initEncoding : function ssi_initEncoding() {
+    // The (UTF-8) encoder used to write to files.
+    XPCOMUtils.defineLazyGetter(this, "_writeFileEncoder", function () {
+      return new TextEncoder();
+    });
+  },
+
+  _initPrefs : function() {
+    XPCOMUtils.defineLazyGetter(this, "_prefBranch", function () {
+      return Services.prefs.getBranch("browser.");
+    });
+
+    // minimal interval between two save operations (in milliseconds)
+    XPCOMUtils.defineLazyGetter(this, "_interval", function () {
+      // used often, so caching/observing instead of fetching on-demand
+      this._prefBranch.addObserver("sessionstore.interval", this, true);
+      return this._prefBranch.getIntPref("sessionstore.interval");
+    });
+
+    // when crash recovery is disabled, session data is not written to disk
+    XPCOMUtils.defineLazyGetter(this, "_resume_from_crash", function () {
+      // get crash recovery state from prefs and allow for proper reaction to state changes
+      this._prefBranch.addObserver("sessionstore.resume_from_crash", this, true);
+      return this._prefBranch.getBoolPref("sessionstore.resume_from_crash");
+    });
+
+    this._max_tabs_undo = this._prefBranch.getIntPref("sessionstore.max_tabs_undo");
+    this._prefBranch.addObserver("sessionstore.max_tabs_undo", this, true);
+    
+    this._max_windows_undo = this._prefBranch.getIntPref("sessionstore.max_windows_undo");
+    this._prefBranch.addObserver("sessionstore.max_windows_undo", this, true);
+    
+    // Straight-up collect the following one-time prefs
+    this._maxConcurrentTabRestores = 
+         Services.prefs.getIntPref("browser.sessionstore.max_concurrent_tabs");
+    // ensure a sane value for concurrency, ignore and set default otherwise
+    if (this._maxConcurrentTabRestores < 1 || this._maxConcurrentTabRestores > 10) {
+      this._maxConcurrentTabRestores = DEFAULT_MAX_CONCURRENT_TAB_RESTORES;
+    }
+    this._cacheBehavior =
+         Services.prefs.getIntPref("browser.sessionstore.cache_behavior");
+    
+  },
+
+  _initWindow: function ssi_initWindow(aWindow) {
+    if (aWindow) {
+      this.onLoad(aWindow);
+    } else if (this._loadState == STATE_STOPPED) {
+      // If init is being called with a null window, it's possible that we
+      // just want to tell sessionstore that a session is live (as is the case
+      // with starting Firefox with -private, for example; see bug 568816),
+      // so we should mark the load state as running to make sure that
+      // things like setBrowserState calls will succeed in restoring the session.
+      this._loadState = STATE_RUNNING;
+    }
+  },
+
+  /**
+   * Start tracking a window.
+   *
+   * This function also initializes the component if it is not
+   * initialized yet.
+   */
+  init: function ssi_init(aWindow) {
+    let self = this;
+    this.initService();
+    return this._promiseInitialization.promise.then(
+      function onSuccess() {
+        self._initWindow(aWindow);
+      }
+    );
+  },
+
+  /**
+   * Called on application shutdown, after notifications:
+   * quit-application-granted, quit-application
+   */
+  _uninit: function ssi_uninit() {
+    // save all data for session resuming
+    if (this._sessionInitialized)
+      this.saveState(true);
+
+    // clear out priority queue in case it's still holding refs
+    TabRestoreQueue.reset();
+
+    // Make sure to break our cycle with the save timer
+    if (this._saveTimer) {
+      this._saveTimer.cancel();
+      this._saveTimer = null;
+    }
+  },
+
+  /**
+   * Handle notifications
+   */
+  observe: function ssi_observe(aSubject, aTopic, aData) {
+    if (this._disabledForMultiProcess)
+      return;
+
+    switch (aTopic) {
+      case "domwindowopened": // catch new windows
+        this.onOpen(aSubject);
+        break;
+      case "domwindowclosed": // catch closed windows
+        this.onClose(aSubject);
+        break;
+      case "quit-application-requested":
+        this.onQuitApplicationRequested();
+        break;
+      case "quit-application-granted":
+        this.onQuitApplicationGranted();
+        break;
+      case "browser-lastwindow-close-granted":
+        this.onLastWindowCloseGranted();
+        break;
+      case "quit-application":
+        this.onQuitApplication(aData);
+        break;
+      case "browser:purge-session-history": // catch sanitization
+        this.onPurgeSessionHistory();
+        break;
+      case "browser:purge-domain-data":
+        this.onPurgeDomainData(aData);
+        break;
+      case "nsPref:changed": // catch pref changes
+        this.onPrefChange(aData);
+        break;
+      case "timer-callback": // timer call back for delayed saving
+        this.onTimerCallback();
+        break;
+    }
+  },
+
+  /**
+   * This method handles incoming messages sent by the session store content
+   * script and thus enables communication with OOP tabs.
+   */
+  receiveMessage: function ssi_receiveMessage(aMessage) {
+    var browser = aMessage.target;
+    var win = browser.ownerDocument.defaultView;
+
+    switch (aMessage.name) {
+      case "SessionStore:pageshow":
+        this.onTabLoad(win, browser);
+        break;
+      case "SessionStore:input":
+        this.onTabInput(win, browser);
+        break;
+      default:
+        debug("received unknown message '" + aMessage.name + "'");
+        break;
+    }
+
+    this._clearRestoringWindows();
+  },
+
+  /* ........ Window Event Handlers .............. */
+
+  /**
+   * Implement nsIDOMEventListener for handling various window and tab events
+   */
+  handleEvent: function ssi_handleEvent(aEvent) {
+    if (this._disabledForMultiProcess)
+      return;
+
+    var win = aEvent.currentTarget.ownerDocument.defaultView;
+    switch (aEvent.type) {
+      case "load":
+        // If __SS_restore_data is set, then we need to restore the document
+        // (form data, scrolling, etc.). This will only happen when a tab is
+        // first restored.
+        let browser = aEvent.currentTarget;
+        if (browser.__SS_restore_data)
+          this.restoreDocument(win, browser, aEvent);
+        this.onTabLoad(win, browser);
+        break;
+      case "TabOpen":
+        this.onTabAdd(win, aEvent.originalTarget);
+        break;
+      case "TabClose":
+        // aEvent.detail determines if the tab was closed by moving to a different window
+        if (!aEvent.detail)
+          this.onTabClose(win, aEvent.originalTarget);
+        this.onTabRemove(win, aEvent.originalTarget);
+        break;
+      case "TabSelect":
+        this.onTabSelect(win);
+        break;
+      case "TabShow":
+        this.onTabShow(win, aEvent.originalTarget);
+        break;
+      case "TabHide":
+        this.onTabHide(win, aEvent.originalTarget);
+        break;
+      case "TabPinned":
+      case "TabUnpinned":
+        this.saveStateDelayed(win);
+        break;
+    }
+
+    this._clearRestoringWindows();
+  },
+
+  /**
+   * If it's the first window load since app start...
+   * - determine if we're reloading after a crash or a forced-restart
+   * - restore window state
+   * - restart downloads
+   * Set up event listeners for this window's tabs
+   * @param aWindow
+   *        Window reference
+   */
+  onLoad: function ssi_onLoad(aWindow) {
+    // return if window has already been initialized
+    if (aWindow && aWindow.__SSi && this._windows[aWindow.__SSi])
+      return;
+
+    // ignore non-browser windows and windows opened while shutting down
+    if (aWindow.document.documentElement.getAttribute("windowtype") != "navigator:browser" ||
+        this._loadState == STATE_QUITTING)
+      return;
+
+    // assign it a unique identifier (timestamp)
+    aWindow.__SSi = "window" + Date.now();
+
+    // and create its data object
+    this._windows[aWindow.__SSi] = { tabs: [], selected: 0, _closedTabs: [], busy: false };
+
+    // and create its internal data object
+    this._internalWindows[aWindow.__SSi] = { hosts: {} }
+
+    let isPrivateWindow = false;
+    if (PrivateBrowsingUtils.isWindowPrivate(aWindow))
+      this._windows[aWindow.__SSi].isPrivate = isPrivateWindow = true;
+    if (!this._isWindowLoaded(aWindow))
+      this._windows[aWindow.__SSi]._restoring = true;
+    if (!aWindow.toolbar.visible)
+      this._windows[aWindow.__SSi].isPopup = true;
+
+    // perform additional initialization when the first window is loading
+    if (this._loadState == STATE_STOPPED) {
+      this._loadState = STATE_RUNNING;
+      this._lastSaveTime = Date.now();
+
+      // restore a crashed session resp. resume the last session if requested
+      if (this._initialState) {
+        if (isPrivateWindow) {
+          // We're starting with a single private window. Save the state we
+          // actually wanted to restore so that we can do it later in case
+          // the user opens another, non-private window.
+          this._deferredInitialState = gSessionStartup.state;
+          delete this._initialState;
+
+          // Nothing to restore now, notify observers things are complete.
+          Services.obs.notifyObservers(null, NOTIFY_WINDOWS_RESTORED, "");
+        } else {
+          // make sure that the restored tabs are first in the window
+          this._initialState._firstTabs = true;
+          this._restoreCount = this._initialState.windows ? this._initialState.windows.length : 0;
+          this.restoreWindow(aWindow, this._initialState,
+                             this._isCmdLineEmpty(aWindow, this._initialState));
+          delete this._initialState;
+
+          // _loadState changed from "stopped" to "running"
+          // force a save operation so that crashes happening during startup are correctly counted
+          this.saveState(true);
+        }
+      }
+      else {
+        // Nothing to restore, notify observers things are complete.
+        Services.obs.notifyObservers(null, NOTIFY_WINDOWS_RESTORED, "");
+
+        // the next delayed save request should execute immediately
+        this._lastSaveTime -= this._interval;
+      }
+    }
+    // this window was opened by _openWindowWithState
+    else if (!this._isWindowLoaded(aWindow)) {
+      let followUp = this._statesToRestore[aWindow.__SS_restoreID].windows.length == 1;
+      this.restoreWindow(aWindow, this._statesToRestore[aWindow.__SS_restoreID], true, followUp);
+    }
+    // The user opened another, non-private window after starting up with
+    // a single private one. Let's restore the session we actually wanted to
+    // restore at startup.
+    else if (this._deferredInitialState && !isPrivateWindow &&
+             aWindow.toolbar.visible) {
+
+      this._deferredInitialState._firstTabs = true;
+      this._restoreCount = this._deferredInitialState.windows ?
+        this._deferredInitialState.windows.length : 0;
+      this.restoreWindow(aWindow, this._deferredInitialState, false);
+      this._deferredInitialState = null;
+    }
+    else if (this._restoreLastWindow && aWindow.toolbar.visible &&
+             this._closedWindows.length && !isPrivateWindow) {
+
+      // default to the most-recently closed window
+      // don't use popup windows
+      let closedWindowState = null;
+      let closedWindowIndex;
+      for (let i = 0; i < this._closedWindows.length; i++) {
+        // Take the first non-popup, point our object at it, and break out.
+        if (!this._closedWindows[i].isPopup) {
+          closedWindowState = this._closedWindows[i];
+          closedWindowIndex = i;
+          break;
+        }
+      }
+
+      if (closedWindowState) {
+        let newWindowState;
+#ifndef XP_MACOSX
+        if (!this._doResumeSession()) {
+#endif
+          // We want to split the window up into pinned tabs and unpinned tabs.
+          // Pinned tabs should be restored. If there are any remaining tabs,
+          // they should be added back to _closedWindows.
+          // We'll cheat a little bit and reuse _prepDataForDeferredRestore
+          // even though it wasn't built exactly for this.
+          let [appTabsState, normalTabsState] =
+            this._prepDataForDeferredRestore({ windows: [closedWindowState] });
+
+          // These are our pinned tabs, which we should restore
+          if (appTabsState.windows.length) {
+            newWindowState = appTabsState.windows[0];
+            delete newWindowState.__lastSessionWindowID;
+          }
+
+          // In case there were no unpinned tabs, remove the window from _closedWindows
+          if (!normalTabsState.windows.length) {
+            this._closedWindows.splice(closedWindowIndex, 1);
+          }
+          // Or update _closedWindows with the modified state
+          else {
+            delete normalTabsState.windows[0].__lastSessionWindowID;
+            this._closedWindows[closedWindowIndex] = normalTabsState.windows[0];
+          }
+#ifndef XP_MACOSX
+        }
+        else {
+          // If we're just restoring the window, make sure it gets removed from
+          // _closedWindows.
+          this._closedWindows.splice(closedWindowIndex, 1);
+          newWindowState = closedWindowState;
+          delete newWindowState.hidden;
+        }
+#endif
+        if (newWindowState) {
+          // Ensure that the window state isn't hidden
+          this._restoreCount = 1;
+          let state = { windows: [newWindowState] };
+          this.restoreWindow(aWindow, state, this._isCmdLineEmpty(aWindow, state));
+        }
+      }
+      // we actually restored the session just now.
+      this._prefBranch.setBoolPref("sessionstore.resume_session_once", false);
+    }
+    if (this._restoreLastWindow && aWindow.toolbar.visible) {
+      // always reset (if not a popup window)
+      // we don't want to restore a window directly after, for example,
+      // undoCloseWindow was executed.
+      this._restoreLastWindow = false;
+    }
+
+    var tabbrowser = aWindow.gBrowser;
+
+    // add tab change listeners to all already existing tabs
+    for (let i = 0; i < tabbrowser.tabs.length; i++) {
+      this.onTabAdd(aWindow, tabbrowser.tabs[i], true);
+    }
+    // notification of tab add/remove/selection/show/hide
+    TAB_EVENTS.forEach(function(aEvent) {
+      tabbrowser.tabContainer.addEventListener(aEvent, this, true);
+    }, this);
+  },
+
+  /**
+   * On window open
+   * @param aWindow
+   *        Window reference
+   */
+  onOpen: function ssi_onOpen(aWindow) {
+    var _this = this;
+    aWindow.addEventListener("load", function(aEvent) {
+      aEvent.currentTarget.removeEventListener("load", arguments.callee, false);
+      _this.onLoad(aEvent.currentTarget);
+    }, false);
+    return;
+  },
+
+  /**
+   * On window close...
+   * - remove event listeners from tabs
+   * - save all window data
+   * @param aWindow
+   *        Window reference
+   */
+  onClose: function ssi_onClose(aWindow) {
+    // this window was about to be restored - conserve its original data, if any
+    let isFullyLoaded = this._isWindowLoaded(aWindow);
+    if (!isFullyLoaded) {
+      if (!aWindow.__SSi)
+        aWindow.__SSi = "window" + Date.now();
+      this._windows[aWindow.__SSi] = this._statesToRestore[aWindow.__SS_restoreID];
+      delete this._statesToRestore[aWindow.__SS_restoreID];
+      delete aWindow.__SS_restoreID;
+    }
+
+    // ignore windows not tracked by SessionStore
+    if (!aWindow.__SSi || !this._windows[aWindow.__SSi]) {
+      return;
+    }
+
+    // notify that the session store will stop tracking this window so that
+    // extensions can store any data about this window in session store before
+    // that's not possible anymore
+    let event = aWindow.document.createEvent("Events");
+    event.initEvent("SSWindowClosing", true, false);
+    aWindow.dispatchEvent(event);
+
+    if (this.windowToFocus && this.windowToFocus == aWindow) {
+      delete this.windowToFocus;
+    }
+
+    var tabbrowser = aWindow.gBrowser;
+
+    TAB_EVENTS.forEach(function(aEvent) {
+      tabbrowser.tabContainer.removeEventListener(aEvent, this, true);
+    }, this);
+
+    // remove the progress listener for this window
+    tabbrowser.removeTabsProgressListener(gRestoreTabsProgressListener);
+
+    let winData = this._windows[aWindow.__SSi];
+    if (this._loadState == STATE_RUNNING) { // window not closed during a regular shut-down
+      // update all window data for a last time
+      this._collectWindowData(aWindow);
+
+      if (isFullyLoaded) {
+        winData.title = aWindow.content.document.title || tabbrowser.selectedTab.label;
+        winData.title = this._replaceLoadingTitle(winData.title, tabbrowser,
+                                                  tabbrowser.selectedTab);
+        let windows = {};
+        windows[aWindow.__SSi] = winData;
+        this._updateCookies(windows);
+      }
+
+#ifndef XP_MACOSX
+      // Until we decide otherwise elsewhere, this window is part of a series
+      // of closing windows to quit.
+      winData._shouldRestore = true;
+#endif
+
+      // Save the window if it has multiple tabs or a single saveable tab and
+      // it's not private.
+      if (!winData.isPrivate && (winData.tabs.length > 1 ||
+          (winData.tabs.length == 1 && this._shouldSaveTabState(winData.tabs[0])))) {
+        // we don't want to save the busy state
+        delete winData.busy;
+
+        this._closedWindows.unshift(winData);
+        this._capClosedWindows();
+      }
+
+      // clear this window from the list
+      delete this._windows[aWindow.__SSi];
+      delete this._internalWindows[aWindow.__SSi];
+
+      // save the state without this window to disk
+      this.saveStateDelayed();
+    }
+
+    for (let i = 0; i < tabbrowser.tabs.length; i++) {
+      this.onTabRemove(aWindow, tabbrowser.tabs[i], true);
+    }
+
+    // Cache the window state until it is completely gone.
+    DyingWindowCache.set(aWindow, winData);
+
+    delete aWindow.__SSi;
+  },
+
+  /**
+   * On quit application requested
+   */
+  onQuitApplicationRequested: function ssi_onQuitApplicationRequested() {
+    // get a current snapshot of all windows
+    this._forEachBrowserWindow(function(aWindow) {
+      this._collectWindowData(aWindow);
+    });
+    // we must cache this because _getMostRecentBrowserWindow will always
+    // return null by the time quit-application occurs
+    var activeWindow = this._getMostRecentBrowserWindow();
+    if (activeWindow)
+      this.activeWindowSSiCache = activeWindow.__SSi || "";
+    this._dirtyWindows = [];
+  },
+
+  /**
+   * On quit application granted
+   */
+  onQuitApplicationGranted: function ssi_onQuitApplicationGranted() {
+    // freeze the data at what we've got (ignoring closing windows)
+    this._loadState = STATE_QUITTING;
+  },
+
+  /**
+   * On last browser window close
+   */
+  onLastWindowCloseGranted: function ssi_onLastWindowCloseGranted() {
+    // last browser window is quitting.
+    // remember to restore the last window when another browser window is opened
+    // do not account for pref(resume_session_once) at this point, as it might be
+    // set by another observer getting this notice after us
+    this._restoreLastWindow = true;
+  },
+
+  /**
+   * On quitting application
+   * @param aData
+   *        String type of quitting
+   */
+  onQuitApplication: function ssi_onQuitApplication(aData) {
+    if (aData == "restart") {
+      this._prefBranch.setBoolPref("sessionstore.resume_session_once", true);
+      // The browser:purge-session-history notification fires after the
+      // quit-application notification so unregister the
+      // browser:purge-session-history notification to prevent clearing
+      // session data on disk on a restart.  It is also unnecessary to
+      // perform any other sanitization processing on a restart as the
+      // browser is about to exit anyway.
+      Services.obs.removeObserver(this, "browser:purge-session-history");
+    }
+    else if (this._resume_session_once_on_shutdown != null) {
+      // if the sessionstore.resume_session_once preference was changed by
+      // saveState because crash recovery is disabled then restore the
+      // preference back to the value it was prior to that.  This will prevent
+      // SessionStore from always restoring the session when crash recovery is
+      // disabled.
+      this._prefBranch.setBoolPref("sessionstore.resume_session_once",
+                                   this._resume_session_once_on_shutdown);
+    }
+
+    if (aData != "restart") {
+      // Throw away the previous session on shutdown
+      this._lastSessionState = null;
+    }
+
+    this._loadState = STATE_QUITTING; // just to be sure
+    this._uninit();
+  },
+
+  /**
+   * On purge of session history
+   */
+  onPurgeSessionHistory: function ssi_onPurgeSessionHistory() {
+    var _this = this;
+    _SessionFile.wipe();
+    // If the browser is shutting down, simply return after clearing the
+    // session data on disk as this notification fires after the
+    // quit-application notification so the browser is about to exit.
+    if (this._loadState == STATE_QUITTING)
+      return;
+    this._lastSessionState = null;
+    let openWindows = {};
+    this._forEachBrowserWindow(function(aWindow) {
+      Array.forEach(aWindow.gBrowser.tabs, function(aTab) {
+        delete aTab.linkedBrowser.__SS_data;
+        delete aTab.linkedBrowser.__SS_tabStillLoading;
+        delete aTab.linkedBrowser.__SS_formDataSaved;
+        delete aTab.linkedBrowser.__SS_hostSchemeData;
+        if (aTab.linkedBrowser.__SS_restoreState)
+          this._resetTabRestoringState(aTab);
+      }, this);
+      openWindows[aWindow.__SSi] = true;
+    });
+    // also clear all data about closed tabs and windows
+    for (let ix in this._windows) {
+      if (ix in openWindows) {
+        this._windows[ix]._closedTabs = [];
+      }
+      else {
+        delete this._windows[ix];
+        delete this._internalWindows[ix];
+      }
+    }
+    // also clear all data about closed windows
+    this._closedWindows = [];
+    // give the tabbrowsers a chance to clear their histories first
+    var win = this._getMostRecentBrowserWindow();
+    if (win)
+      win.setTimeout(function() { _this.saveState(true); }, 0);
+    else if (this._loadState == STATE_RUNNING)
+      this.saveState(true);
+    // Delete the private browsing backed up state, if any
+    if ("_stateBackup" in this)
+      delete this._stateBackup;
+
+    this._clearRestoringWindows();
+  },
+
+  /**
+   * On purge of domain data
+   * @param aData
+   *        String domain data
+   */
+  onPurgeDomainData: function ssi_onPurgeDomainData(aData) {
+    // does a session history entry contain a url for the given domain?
+    function containsDomain(aEntry) {
+      try {
+        if (this._getURIFromString(aEntry.url).host.hasRootDomain(aData))
+          return true;
+      }
+      catch (ex) { /* url had no host at all */ }
+      return aEntry.children && aEntry.children.some(containsDomain, this);
+    }
+    // remove all closed tabs containing a reference to the given domain
+    for (let ix in this._windows) {
+      let closedTabs = this._windows[ix]._closedTabs;
+      for (let i = closedTabs.length - 1; i >= 0; i--) {
+        if (closedTabs[i].state.entries.some(containsDomain, this))
+          closedTabs.splice(i, 1);
+      }
+    }
+    // remove all open & closed tabs containing a reference to the given
+    // domain in closed windows
+    for (let ix = this._closedWindows.length - 1; ix >= 0; ix--) {
+      let closedTabs = this._closedWindows[ix]._closedTabs;
+      let openTabs = this._closedWindows[ix].tabs;
+      let openTabCount = openTabs.length;
+      for (let i = closedTabs.length - 1; i >= 0; i--)
+        if (closedTabs[i].state.entries.some(containsDomain, this))
+          closedTabs.splice(i, 1);
+      for (let j = openTabs.length - 1; j >= 0; j--) {
+        if (openTabs[j].entries.some(containsDomain, this)) {
+          openTabs.splice(j, 1);
+          if (this._closedWindows[ix].selected > j)
+            this._closedWindows[ix].selected--;
+        }
+      }
+      if (openTabs.length == 0) {
+        this._closedWindows.splice(ix, 1);
+      }
+      else if (openTabs.length != openTabCount) {
+        // Adjust the window's title if we removed an open tab
+        let selectedTab = openTabs[this._closedWindows[ix].selected - 1];
+        // some duplication from restoreHistory - make sure we get the correct title
+        let activeIndex = (selectedTab.index || selectedTab.entries.length) - 1;
+        if (activeIndex >= selectedTab.entries.length)
+          activeIndex = selectedTab.entries.length - 1;
+        this._closedWindows[ix].title = selectedTab.entries[activeIndex].title;
+      }
+    }
+    if (this._loadState == STATE_RUNNING)
+      this.saveState(true);
+
+    this._clearRestoringWindows();
+  },
+
+  /**
+   * On preference change
+   * @param aData
+   *        String preference changed
+   */
+  onPrefChange: function ssi_onPrefChange(aData) {
+    switch (aData) {
+      // if the user decreases the max number of closed tabs they want
+      // preserved update our internal states to match that max
+      case "sessionstore.max_tabs_undo":
+        this._max_tabs_undo = this._prefBranch.getIntPref("sessionstore.max_tabs_undo");
+        for (let ix in this._windows) {
+          this._windows[ix]._closedTabs.splice(this._max_tabs_undo, this._windows[ix]._closedTabs.length);
+        }
+        break;
+      case "sessionstore.max_windows_undo":
+        this._max_windows_undo = this._prefBranch.getIntPref("sessionstore.max_windows_undo");
+        this._capClosedWindows();
+        break;
+      case "sessionstore.interval":
+        this._interval = this._prefBranch.getIntPref("sessionstore.interval");
+        // reset timer and save
+        if (this._saveTimer) {
+          this._saveTimer.cancel();
+          this._saveTimer = null;
+        }
+        this.saveStateDelayed(null, -1);
+        break;
+      case "sessionstore.resume_from_crash":
+        this._resume_from_crash = this._prefBranch.getBoolPref("sessionstore.resume_from_crash");
+        // restore original resume_session_once preference if set in saveState
+        if (this._resume_session_once_on_shutdown != null) {
+          this._prefBranch.setBoolPref("sessionstore.resume_session_once",
+                                       this._resume_session_once_on_shutdown);
+          this._resume_session_once_on_shutdown = null;
+        }
+        // either create the file with crash recovery information or remove it
+        // (when _loadState is not STATE_RUNNING, that file is used for session resuming instead)
+        if (!this._resume_from_crash)
+          _SessionFile.wipe();
+        this.saveState(true);
+        break;
+    }
+  },
+
+  /**
+   * On timer callback
+   */
+  onTimerCallback: function ssi_onTimerCallback() {
+    this._saveTimer = null;
+    this.saveState();
+  },
+
+  /**
+   * set up listeners for a new tab
+   * @param aWindow
+   *        Window reference
+   * @param aTab
+   *        Tab reference
+   * @param aNoNotification
+   *        bool Do not save state if we're updating an existing tab
+   */
+  onTabAdd: function ssi_onTabAdd(aWindow, aTab, aNoNotification) {
+    let browser = aTab.linkedBrowser;
+    browser.addEventListener("load", this, true);
+
+    let mm = browser.messageManager;
+    MESSAGES.forEach(msg => mm.addMessageListener(msg, this));
+
+    if (!aNoNotification) {
+      this.saveStateDelayed(aWindow);
+    }
+  },
+
+  /**
+   * remove listeners for a tab
+   * @param aWindow
+   *        Window reference
+   * @param aTab
+   *        Tab reference
+   * @param aNoNotification
+   *        bool Do not save state if we're updating an existing tab
+   */
+  onTabRemove: function ssi_onTabRemove(aWindow, aTab, aNoNotification) {
+    let browser = aTab.linkedBrowser;
+    browser.removeEventListener("load", this, true);
+
+    let mm = browser.messageManager;
+    MESSAGES.forEach(msg => mm.removeMessageListener(msg, this));
+
+    delete browser.__SS_data;
+    delete browser.__SS_tabStillLoading;
+    delete browser.__SS_formDataSaved;
+    delete browser.__SS_hostSchemeData;
+
+    // If this tab was in the middle of restoring or still needs to be restored,
+    // we need to reset that state. If the tab was restoring, we will attempt to
+    // restore the next tab.
+    let previousState = browser.__SS_restoreState;
+    if (previousState) {
+      this._resetTabRestoringState(aTab);
+      if (previousState == TAB_STATE_RESTORING)
+        this.restoreNextTab();
+    }
+
+    if (!aNoNotification) {
+      this.saveStateDelayed(aWindow);
+    }
+  },
+
+  /**
+   * When a tab closes, collect its properties
+   * @param aWindow
+   *        Window reference
+   * @param aTab
+   *        Tab reference
+   */
+  onTabClose: function ssi_onTabClose(aWindow, aTab) {
+    // notify the tabbrowser that the tab state will be retrieved for the last time
+    // (so that extension authors can easily set data on soon-to-be-closed tabs)
+    var event = aWindow.document.createEvent("Events");
+    event.initEvent("SSTabClosing", true, false);
+    aTab.dispatchEvent(event);
+
+    // don't update our internal state if we don't have to
+    if (this._max_tabs_undo == 0) {
+      return;
+    }
+
+    // make sure that the tab related data is up-to-date
+    var tabState = this._collectTabData(aTab);
+    this._updateTextAndScrollDataForTab(aWindow, aTab.linkedBrowser, tabState);
+
+    // store closed-tab data for undo
+    if (this._shouldSaveTabState(tabState)) {
+      let tabTitle = aTab.label;
+      let tabbrowser = aWindow.gBrowser;
+      tabTitle = this._replaceLoadingTitle(tabTitle, tabbrowser, aTab);
+
+      this._windows[aWindow.__SSi]._closedTabs.unshift({
+        state: tabState,
+        title: tabTitle,
+        image: tabbrowser.getIcon(aTab),
+        pos: aTab._tPos
+      });
+      var length = this._windows[aWindow.__SSi]._closedTabs.length;
+      if (length > this._max_tabs_undo)
+        this._windows[aWindow.__SSi]._closedTabs.splice(this._max_tabs_undo, length - this._max_tabs_undo);
+    }
+  },
+
+  /**
+   * When a tab loads, save state.
+   * @param aWindow
+   *        Window reference
+   * @param aBrowser
+   *        Browser reference
+   */
+  onTabLoad: function ssi_onTabLoad(aWindow, aBrowser) {
+    // react on "load" and solitary "pageshow" events (the first "pageshow"
+    // following "load" is too late for deleting the data caches)
+    // It's possible to get a load event after calling stop on a browser (when
+    // overwriting tabs). We want to return early if the tab hasn't been restored yet.
+    if (aBrowser.__SS_restoreState &&
+        aBrowser.__SS_restoreState == TAB_STATE_NEEDS_RESTORE) {
+      return;
+    }
+
+    delete aBrowser.__SS_data;
+    delete aBrowser.__SS_tabStillLoading;
+    delete aBrowser.__SS_formDataSaved;
+    this.saveStateDelayed(aWindow);
+
+  },
+
+  /**
+   * Called when a browser sends the "input" notification
+   * @param aWindow
+   *        Window reference
+   * @param aBrowser
+   *        Browser reference
+   */
+  onTabInput: function ssi_onTabInput(aWindow, aBrowser) {
+    // deleting __SS_formDataSaved will cause us to recollect form data
+    delete aBrowser.__SS_formDataSaved;
+
+    this.saveStateDelayed(aWindow, 3000);
+  },
+
+  /**
+   * When a tab is selected, save session data
+   * @param aWindow
+   *        Window reference
+   */
+  onTabSelect: function ssi_onTabSelect(aWindow) {
+    if (this._loadState == STATE_RUNNING) {
+      this._windows[aWindow.__SSi].selected = aWindow.gBrowser.tabContainer.selectedIndex;
+
+      let tab = aWindow.gBrowser.selectedTab;
+      // If __SS_restoreState is still on the browser and it is
+      // TAB_STATE_NEEDS_RESTORE, then then we haven't restored
+      // this tab yet. Explicitly call restoreTab to kick off the restore.
+      if (tab.linkedBrowser.__SS_restoreState &&
+          tab.linkedBrowser.__SS_restoreState == TAB_STATE_NEEDS_RESTORE)
+        this.restoreTab(tab);
+
+    }
+  },
+
+  onTabShow: function ssi_onTabShow(aWindow, aTab) {
+    // If the tab hasn't been restored yet, move it into the right bucket
+    if (aTab.linkedBrowser.__SS_restoreState &&
+        aTab.linkedBrowser.__SS_restoreState == TAB_STATE_NEEDS_RESTORE) {
+      TabRestoreQueue.hiddenToVisible(aTab);
+
+      // let's kick off tab restoration again to ensure this tab gets restored
+      // with "restore_hidden_tabs" == false (now that it has become visible)
+      this.restoreNextTab();
+    }
+
+    // Default delay of 2 seconds gives enough time to catch multiple TabShow
+    // events due to changing groups in Panorama.
+    this.saveStateDelayed(aWindow);
+  },
+
+  onTabHide: function ssi_onTabHide(aWindow, aTab) {
+    // If the tab hasn't been restored yet, move it into the right bucket
+    if (aTab.linkedBrowser.__SS_restoreState &&
+        aTab.linkedBrowser.__SS_restoreState == TAB_STATE_NEEDS_RESTORE) {
+      TabRestoreQueue.visibleToHidden(aTab);
+    }
+
+    // Default delay of 2 seconds gives enough time to catch multiple TabHide
+    // events due to changing groups in Panorama.
+    this.saveStateDelayed(aWindow);
+  },
+
+  /* ........ nsISessionStore API .............. */
+
+  getBrowserState: function ssi_getBrowserState() {
+    return this._toJSONString(this._getCurrentState());
+  },
+
+  setBrowserState: function ssi_setBrowserState(aState) {
+    this._handleClosedWindows();
+
+    try {
+      var state = JSON.parse(aState);
+    }
+    catch (ex) { /* invalid state object - don't restore anything */ }
+    if (!state || !state.windows)
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    this._browserSetState = true;
+
+    // Make sure the priority queue is emptied out
+    this._resetRestoringState();
+
+    var window = this._getMostRecentBrowserWindow();
+    if (!window) {
+      this._restoreCount = 1;
+      this._openWindowWithState(state);
+      return;
+    }
+
+    // close all other browser windows
+    this._forEachBrowserWindow(function(aWindow) {
+      if (aWindow != window) {
+        aWindow.close();
+        this.onClose(aWindow);
+      }
+    });
+
+    // make sure closed window data isn't kept
+    this._closedWindows = [];
+
+    // determine how many windows are meant to be restored
+    this._restoreCount = state.windows ? state.windows.length : 0;
+
+    // restore to the given state
+    this.restoreWindow(window, state, true);
+  },
+
+  getWindowState: function ssi_getWindowState(aWindow) {
+    if ("__SSi" in aWindow) {
+      return this._toJSONString(this._getWindowState(aWindow));
+    }
+
+    if (DyingWindowCache.has(aWindow)) {
+      let data = DyingWindowCache.get(aWindow);
+      return this._toJSONString({ windows: [data] });
+    }
+
+    throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+  },
+
+  setWindowState: function ssi_setWindowState(aWindow, aState, aOverwrite) {
+    if (!aWindow.__SSi)
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    this.restoreWindow(aWindow, aState, aOverwrite);
+  },
+
+  getTabState: function ssi_getTabState(aTab) {
+    if (!aTab.ownerDocument || !aTab.ownerDocument.defaultView.__SSi)
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    var tabState = this._collectTabData(aTab);
+
+    var window = aTab.ownerDocument.defaultView;
+    this._updateTextAndScrollDataForTab(window, aTab.linkedBrowser, tabState);
+
+    return this._toJSONString(tabState);
+  },
+
+  setTabState: function ssi_setTabState(aTab, aState) {
+    var tabState = JSON.parse(aState);
+    if (!tabState.entries || !aTab.ownerDocument || !aTab.ownerDocument.defaultView.__SSi)
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    var window = aTab.ownerDocument.defaultView;
+    this._setWindowStateBusy(window);
+    this.restoreHistoryPrecursor(window, [aTab], [tabState], 0, 0, 0);
+  },
+
+  duplicateTab: function ssi_duplicateTab(aWindow, aTab, aDelta) {
+    if (!aTab.ownerDocument || !aTab.ownerDocument.defaultView.__SSi ||
+        !aWindow.getBrowser)
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    var tabState = this._collectTabData(aTab, true);
+    var sourceWindow = aTab.ownerDocument.defaultView;
+    this._updateTextAndScrollDataForTab(sourceWindow, aTab.linkedBrowser, tabState, true);
+    tabState.index += aDelta;
+    tabState.index = Math.max(1, Math.min(tabState.index, tabState.entries.length));
+    tabState.pinned = false;
+
+    this._setWindowStateBusy(aWindow);
+    let newTab = aTab == aWindow.gBrowser.selectedTab ?
+      aWindow.gBrowser.addTab(null, {relatedToCurrent: true, ownerTab: aTab}) :
+      aWindow.gBrowser.addTab();
+
+    this.restoreHistoryPrecursor(aWindow, [newTab], [tabState], 0, 0, 0,
+                                 true /* Load this tab right away. */);
+
+    return newTab;
+  },
+
+  getClosedTabCount: function ssi_getClosedTabCount(aWindow) {
+    if ("__SSi" in aWindow) {
+      return this._windows[aWindow.__SSi]._closedTabs.length;
+    }
+
+    if (DyingWindowCache.has(aWindow)) {
+      return DyingWindowCache.get(aWindow)._closedTabs.length;
+    }
+
+    throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+  },
+
+  getClosedTabData: function ssi_getClosedTabDataAt(aWindow) {
+    if ("__SSi" in aWindow) {
+      return this._toJSONString(this._windows[aWindow.__SSi]._closedTabs);
+    }
+
+    if (DyingWindowCache.has(aWindow)) {
+      let data = DyingWindowCache.get(aWindow);
+      return this._toJSONString(data._closedTabs);
+    }
+
+    throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+  },
+
+  undoCloseTab: function ssi_undoCloseTab(aWindow, aIndex) {
+    if (!aWindow.__SSi)
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    var closedTabs = this._windows[aWindow.__SSi]._closedTabs;
+
+    // default to the most-recently closed tab
+    aIndex = aIndex || 0;
+    if (!(aIndex in closedTabs))
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    // fetch the data of closed tab, while removing it from the array
+    let closedTab = closedTabs.splice(aIndex, 1).shift();
+    let closedTabState = closedTab.state;
+
+    this._setWindowStateBusy(aWindow);
+    // create a new tab
+    let tabbrowser = aWindow.gBrowser;
+    let tab = tabbrowser.addTab();
+
+    // restore tab content
+    this.restoreHistoryPrecursor(aWindow, [tab], [closedTabState], 1, 0, 0);
+
+    // restore the tab's position
+    tabbrowser.moveTabTo(tab, closedTab.pos);
+
+    // focus the tab's content area (bug 342432)
+    tab.linkedBrowser.focus();
+
+    return tab;
+  },
+
+  forgetClosedTab: function ssi_forgetClosedTab(aWindow, aIndex) {
+    if (!aWindow.__SSi)
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    var closedTabs = this._windows[aWindow.__SSi]._closedTabs;
+
+    // default to the most-recently closed tab
+    aIndex = aIndex || 0;
+    if (!(aIndex in closedTabs))
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    // remove closed tab from the array
+    closedTabs.splice(aIndex, 1);
+  },
+
+  getClosedWindowCount: function ssi_getClosedWindowCount() {
+    return this._closedWindows.length;
+  },
+
+  getClosedWindowData: function ssi_getClosedWindowData() {
+    return this._toJSONString(this._closedWindows);
+  },
+
+  undoCloseWindow: function ssi_undoCloseWindow(aIndex) {
+    if (!(aIndex in this._closedWindows))
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    // reopen the window
+    let state = { windows: this._closedWindows.splice(aIndex, 1) };
+    let window = this._openWindowWithState(state);
+    this.windowToFocus = window;
+    return window;
+  },
+
+  forgetClosedWindow: function ssi_forgetClosedWindow(aIndex) {
+    // default to the most-recently closed window
+    aIndex = aIndex || 0;
+    if (!(aIndex in this._closedWindows))
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+
+    // remove closed window from the array
+    this._closedWindows.splice(aIndex, 1);
+  },
+
+  getWindowValue: function ssi_getWindowValue(aWindow, aKey) {
+    if ("__SSi" in aWindow) {
+      var data = this._windows[aWindow.__SSi].extData || {};
+      return data[aKey] || "";
+    }
+
+    if (DyingWindowCache.has(aWindow)) {
+      let data = DyingWindowCache.get(aWindow).extData || {};
+      return data[aKey] || "";
+    }
+
+    throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+  },
+
+  setWindowValue: function ssi_setWindowValue(aWindow, aKey, aStringValue) {
+    if (aWindow.__SSi) {
+      if (!this._windows[aWindow.__SSi].extData) {
+        this._windows[aWindow.__SSi].extData = {};
+      }
+      this._windows[aWindow.__SSi].extData[aKey] = aStringValue;
+      this.saveStateDelayed(aWindow);
+    }
+    else {
+      throw (Components.returnCode = Cr.NS_ERROR_INVALID_ARG);
+    }
+  },
+
+  deleteWindowValue: function ssi_deleteWindowValue(aWindow, aKey) {
+    if (aWindow.__SSi && this._windows[aWindow.__SSi].extData &&
+        this._windows[aWindow.__SSi].extData[aKey])
+      delete this._windows[aWindow.__SSi].extData[aKey];
+  },
+
+  getTabValue: function ssi_getTabValue(aTab, aKey) {
+    let data = {};
+    if (aTab.__SS_extdata) {
+      data = aTab.__SS_extdata;
+    }
+    else if (aTab.linkedBrowser.__SS_data && aTab.linkedBrowser.__SS_data.extData) {
+      // If the tab hasn't been fully restored, get the data from the to-be-restored data
+      data = aTab.linkedBrowser.__SS_data.extData;
+    }
+    return data[aKey] || "";
+  },
+
+  setTabValue: function ssi_setTabValue(aTab, aKey, aStringValue) {
+    // If the tab hasn't been restored, then set the data there, otherwise we
+    // could lose newly added data.
+    let saveTo;
+    if (aTab.__SS_extdata) {
+      saveTo = aTab.__SS_extdata;
+    }
+    else if (aTab.linkedBrowser.__SS_data && aTab.linkedBrowser.__SS_data.extData) {
+      saveTo = aTab.linkedBrowser.__SS_data.extData;
+    }
+    else {
+      aTab.__SS_extdata = {};
+      saveTo = aTab.__SS_extdata;
+    }
+    saveTo[aKey] = aStringValue;
+    this.saveStateDelayed(aTab.ownerDocument.defaultView);
+  },
+
+  deleteTabValue: function ssi_deleteTabValue(aTab, aKey) {
+    // We want to make sure that if data is accessed early, we attempt to delete
+    // that data from __SS_data as well. Otherwise we'll throw in cases where
+    // data can be set or read.
+    let deleteFrom;
+    if (aTab.__SS_extdata) {
+      deleteFrom = aTab.__SS_extdata;
+    }
+    else if (aTab.linkedBrowser.__SS_data && aTab.linkedBrowser.__SS_data.extData) {
+      deleteFrom = aTab.linkedBrowser.__SS_data.extData;
+    }
+
+    if (deleteFrom && deleteFrom[aKey])
+      delete deleteFrom[aKey];
+  },
+
+  persistTabAttribute: function ssi_persistTabAttribute(aName) {
+    if (TabAttributes.persist(aName)) {
+      this.saveStateDelayed();
+    }
+  },
+
+  /**
+   * Restores the session state stored in _lastSessionState. This will attempt
+   * to merge data into the current session. If a window was opened at startup
+   * with pinned tab(s), then the remaining data from the previous session for
+   * that window will be opened into that winddow. Otherwise new windows will
+   * be opened.
+   */
+  restoreLastSession: function ssi_restoreLastSession() {
+    // Use the public getter since it also checks PB mode
+    if (!this.canRestoreLastSession)
+      throw (Components.returnCode = Cr.NS_ERROR_FAILURE);
+
+    // First collect each window with its id...
+    let windows = {};
+    this._forEachBrowserWindow(function(aWindow) {
+      if (aWindow.__SS_lastSessionWindowID)
+        windows[aWindow.__SS_lastSessionWindowID] = aWindow;
+    });
+
+    let lastSessionState = this._lastSessionState;
+
+    // This shouldn't ever be the case...
+    if (!lastSessionState.windows.length)
+      throw (Components.returnCode = Cr.NS_ERROR_UNEXPECTED);
+
+    // We're technically doing a restore, so set things up so we send the
+    // notification when we're done. We want to send "sessionstore-browser-state-restored".
+    this._restoreCount = lastSessionState.windows.length;
+    this._browserSetState = true;
+
+    // We want to re-use the last opened window instead of opening a new one in
+    // the case where it's "empty" and not associated with a window in the session.
+    // We will do more processing via _prepWindowToRestoreInto if we need to use
+    // the lastWindow.
+    let lastWindow = this._getMostRecentBrowserWindow();
+    let canUseLastWindow = lastWindow &&
+                           !lastWindow.__SS_lastSessionWindowID;
+
+    // Restore into windows or open new ones as needed.
+    for (let i = 0; i < lastSessionState.windows.length; i++) {
+      let winState = lastSessionState.windows[i];
+      let lastSessionWindowID = winState.__lastSessionWindowID;
+      // delete lastSessionWindowID so we don't add that to the window again
+      delete winState.__lastSessionWindowID;
+
+      // See if we can use an open window. First try one that is associated with
+      // the state we're trying to restore and then fallback to the last selected
+      // window.
+      let windowToUse = windows[lastSessionWindowID];
+      if (!windowToUse && canUseLastWindow) {
+        windowToUse = lastWindow;
+        canUseLastWindow = false;
+      }
+
+      let [canUseWindow, canOverwriteTabs] = this._prepWindowToRestoreInto(windowToUse);
+
+      // If there's a window already open that we can restore into, use that
+      if (canUseWindow) {
+        // Since we're not overwriting existing tabs, we want to merge _closedTabs,
+        // putting existing ones first. Then make sure we're respecting the max pref.
+        if (winState._closedTabs && winState._closedTabs.length) {
+          let curWinState = this._windows[windowToUse.__SSi];
+          curWinState._closedTabs = curWinState._closedTabs.concat(winState._closedTabs);
+          curWinState._closedTabs.splice(this._prefBranch.getIntPref("sessionstore.max_tabs_undo"), curWinState._closedTabs.length);
+        }
+
+        // Restore into that window - pretend it's a followup since we'll already
+        // have a focused window.
+        //XXXzpao This is going to merge extData together (taking what was in
+        //        winState over what is in the window already. The hack we have
+        //        in _preWindowToRestoreInto will prevent most (all?) Panorama
+        //        weirdness but we will still merge other extData.
+        //        Bug 588217 should make this go away by merging the group data.
+        this.restoreWindow(windowToUse, { windows: [winState] }, canOverwriteTabs, true);
+      }
+      else {
+        this._openWindowWithState({ windows: [winState] });
+      }
+    }
+
+    // Merge closed windows from this session with ones from last session
+    if (lastSessionState._closedWindows) {
+      this._closedWindows = this._closedWindows.concat(lastSessionState._closedWindows);
+      this._capClosedWindows();
+    }
+
+#ifdef MOZ_DEVTOOLS
+    // Scratchpad
+    if (lastSessionState.scratchpads) {
+      ScratchpadManager.restoreSession(lastSessionState.scratchpads);
+    }
+
+    // The Browser Console
+    if (lastSessionState.browserConsole) {
+      HUDService.restoreBrowserConsoleSession();
+    }
+#endif
+
+    // Set data that persists between sessions
+    this._recentCrashes = lastSessionState.session &&
+                          lastSessionState.session.recentCrashes || 0;
+    this._sessionStartTime = lastSessionState.session &&
+                             lastSessionState.session.startTime ||
+                             this._sessionStartTime;
+
+    this._lastSessionState = null;
+  },
+
+  /**
+   * See if aWindow is usable for use when restoring a previous session via
+   * restoreLastSession. If usable, prepare it for use.
+   *
+   * @param aWindow
+   *        the window to inspect & prepare
+   * @returns [canUseWindow, canOverwriteTabs]
+   *          canUseWindow: can the window be used to restore into
+   *          canOverwriteTabs: all of the current tabs are home pages and we
+   *                            can overwrite them
+   */
+  _prepWindowToRestoreInto: function ssi_prepWindowToRestoreInto(aWindow) {
+    if (!aWindow)
+      return [false, false];
+
+    let event = aWindow.document.createEvent("Events");
+    event.initEvent("SSRestoreIntoWindow", true, true);
+
+    // Check if we can use the window.
+    if (!aWindow.dispatchEvent(event))
+      return [false, false];
+
+    // We might be able to overwrite the existing tabs instead of just adding
+    // the previous session's tabs to the end. This will be set if possible.
+    let canOverwriteTabs = false;
+
+    // Look at the open tabs in comparison to home pages. If all the tabs are
+    // home pages then we'll end up overwriting all of them. Otherwise we'll
+    // just close the tabs that match home pages. Tabs with the about:blank
+    // URI will always be overwritten.
+    let homePages = ["about:blank"];
+    let removableTabs = [];
+    let tabbrowser = aWindow.gBrowser;
+    let normalTabsLen = tabbrowser.tabs.length - tabbrowser._numPinnedTabs;
+    let startupPref = this._prefBranch.getIntPref("startup.page");
+    if (startupPref == 1)
+      homePages = homePages.concat(aWindow.gHomeButton.getHomePage().split("|"));
+
+    for (let i = tabbrowser._numPinnedTabs; i < tabbrowser.tabs.length; i++) {
+      let tab = tabbrowser.tabs[i];
+      if (homePages.indexOf(tab.linkedBrowser.currentURI.spec) != -1) {
+        removableTabs.push(tab);
+      }
+    }
+
+    if (tabbrowser.tabs.length == removableTabs.length) {
+      canOverwriteTabs = true;
+    }
+    else {
+      // If we're not overwriting all of the tabs, then close the home tabs.
+      for (let i = removableTabs.length - 1; i >= 0; i--) {
+        tabbrowser.removeTab(removableTabs.pop(), { animate: false });
+      }
+    }
+
+    return [true, canOverwriteTabs];
+  },
+
+  /* ........ Saving Functionality .............. */
+
+  /**
+   * Store all session data for a window
+   * @param aWindow
+   *        Window reference
+   */
+  _saveWindowHistory: function ssi_saveWindowHistory(aWindow) {
+    var tabbrowser = aWindow.gBrowser;
+    var tabs = tabbrowser.tabs;
+    var tabsData = this._windows[aWindow.__SSi].tabs = [];
+
+    for (var i = 0; i < tabs.length; i++)
+      tabsData.push(this._collectTabData(tabs[i]));
+
+    this._windows[aWindow.__SSi].selected = tabbrowser.mTabBox.selectedIndex + 1;
+  },
+
+  /**
+   * Collect data related to a single tab
+   * @param aTab
+   *        tabbrowser tab
+   * @param aFullData
+   *        always return privacy sensitive data (use with care)
+   * @returns object
+   */
+  _collectTabData: function ssi_collectTabData(aTab, aFullData) {
+    var tabData = { entries: [], lastAccessed: aTab.lastAccessed };
+    var browser = aTab.linkedBrowser;
+
+    if (!browser || !browser.currentURI)
+      // can happen when calling this function right after .addTab()
+      return tabData;
+    else if (browser.__SS_data && browser.__SS_tabStillLoading) {
+      // use the data to be restored when the tab hasn't been completely loaded
+      tabData = browser.__SS_data;
+      if (aTab.pinned)
+        tabData.pinned = true;
+      else
+        delete tabData.pinned;
+      tabData.hidden = aTab.hidden;
+
+      // If __SS_extdata is set then we'll use that since it might be newer.
+      if (aTab.__SS_extdata)
+        tabData.extData = aTab.__SS_extdata;
+      // If it exists but is empty then a key was likely deleted. In that case just
+      // delete extData.
+      if (tabData.extData && !Object.keys(tabData.extData).length)
+        delete tabData.extData;
+      return tabData;
+    }
+
+    var history = null;
+    try {
+      history = browser.sessionHistory;
+    }
+    catch (ex) { } // this could happen if we catch a tab during (de)initialization
+
+    // Limit number of back/forward button history entries to save
+    let oldest, newest;
+    let maxSerializeBack = this._prefBranch.getIntPref("sessionstore.max_serialize_back");
+    if (maxSerializeBack >= 0) {
+      oldest = Math.max(0, history.index - maxSerializeBack);
+    } else { // History.getEntryAtIndex(0, ...) is the oldest.
+      oldest = 0;
+    }
+    let maxSerializeFwd = this._prefBranch.getIntPref("sessionstore.max_serialize_forward");
+    if (maxSerializeFwd >= 0) {
+      newest = Math.min(history.count - 1, history.index + maxSerializeFwd);
+    } else { // History.getEntryAtIndex(history.count - 1, ...) is the newest.
+      newest = history.count - 1;
+    }
+
+    // XXXzeniko anchor navigation doesn't reset __SS_data, so we could reuse
+    //           data even when we shouldn't (e.g. Back, different anchor)
+    // Warning: this is required to save form data and scrolling position!
+    if (history && browser.__SS_data &&
+        browser.__SS_data.entries[history.index] &&
+        browser.__SS_data.entries[history.index].url == browser.currentURI.spec &&
+        history.index < this._sessionhistory_max_entries - 1 && !aFullData) {
+      try {
+        tabData.entries = browser.__SS_data.entries.slice(oldest, newest + 1);
+      }
+      catch (ex) {
+        // No errors are expected above, but we use try-catch to keep sessionstore.js safe
+        NS_ASSERT(false, "SessionStore failed to slice history from browser.__SS_data");
+      }
+
+      // Set the one-based index of the currently active tab, ensuring it isn't out of bounds
+      tabData.index = Math.min(history.index - oldest + 1, tabData.entries.length);
+    }
+    else if (history && history.count > 0) {
+      browser.__SS_hostSchemeData = [];
+      try {
+        for (var j = oldest; j <= newest; j++) {
+          let entry = this._serializeHistoryEntry(history.getEntryAtIndex(j, false),
+                                                  aFullData, aTab.pinned, browser.__SS_hostSchemeData);
+          tabData.entries.push(entry);
+        }
+      }
+      catch (ex) {
+        // In some cases, getEntryAtIndex will throw. This seems to be due to
+        // history.count being higher than it should be. By doing this in a
+        // try-catch, we'll update history to where it breaks, assert for
+        // non-release builds, and still save sessionstore.js.
+        NS_ASSERT(false, "SessionStore failed gathering complete history " +
+                         "for the focused window/tab. See bug 669196.");
+      }
+
+      // Set the one-based index of the currently active tab, ensuring it isn't out of bounds
+      tabData.index = Math.min(history.index - oldest + 1, tabData.entries.length);
+
+      // make sure not to cache privacy sensitive data which shouldn't get out
+      if (!aFullData)
+        browser.__SS_data = tabData;
+    }
+    else if (browser.currentURI.spec != "about:blank" ||
+             browser.contentDocument.body.hasChildNodes()) {
+      tabData.entries[0] = { url: browser.currentURI.spec };
+      tabData.index = 1;
+    }
+
+    // If there is a userTypedValue set, then either the user has typed something
+    // in the URL bar, or a new tab was opened with a URI to load. userTypedClear
+    // is used to indicate whether the tab was in some sort of loading state with
+    // userTypedValue.
+    if (browser.userTypedValue) {
+      tabData.userTypedValue = browser.userTypedValue;
+      // We always used to keep track of the loading state as an integer, where
+      // '0' indicated the user had typed since the last load (or no load was
+      // ongoing), and any positive value indicated we had started a load since
+      // the last time the user typed in the URL bar. Mimic this to keep the
+      // session store representation in sync, even though we now represent this
+      // more explicitly:
+      tabData.userTypedClear = browser.didStartLoadSinceLastUserTyping() ? 1 : 0;
+    } else {
+      delete tabData.userTypedValue;
+      delete tabData.userTypedClear;
+    }
+
+    if (aTab.pinned)
+      tabData.pinned = true;
+    else
+      delete tabData.pinned;
+    tabData.hidden = aTab.hidden;
+
+    var disallow = [];
+    for (let cap of gDocShellCapabilities(browser.docShell))
+      if (!browser.docShell["allow" + cap])
+        disallow.push(cap);
+    if (disallow.length > 0)
+      tabData.disallow = disallow.join(",");
+    else if (tabData.disallow)
+      delete tabData.disallow;
+
+    // Save tab attributes.
+    tabData.attributes = TabAttributes.get(aTab);
+
+    // Store the tab icon.
+    let tabbrowser = aTab.ownerDocument.defaultView.gBrowser;
+    tabData.image = tabbrowser.getIcon(aTab);
+
+    if (aTab.__SS_extdata)
+      tabData.extData = aTab.__SS_extdata;
+    else if (tabData.extData)
+      delete tabData.extData;
+
+    if (history && browser.docShell instanceof Ci.nsIDocShell) {
+      let storageData = SessionStorage.serialize(browser.docShell, aFullData)
+      if (Object.keys(storageData).length)
+        tabData.storage = storageData;
+    }
+
+    return tabData;
+  },
+
+  /**
+   * Get an object that is a serialized representation of a History entry
+   * Used for data storage
+   * @param aEntry
+   *        nsISHEntry instance
+   * @param aFullData
+   *        always return privacy sensitive data (use with care)
+   * @param aIsPinned
+   *        the tab is pinned and should be treated differently for privacy
+   * @param aHostSchemeData
+   *        an array of objects with host & scheme keys
+   * @returns object
+   */
+  _serializeHistoryEntry:
+    function ssi_serializeHistoryEntry(aEntry, aFullData, aIsPinned, aHostSchemeData) {
+    var entry = { url: aEntry.URI.spec };
+
+    try {
+      // throwing is expensive, we know that about: pages will throw
+      if (entry.url.indexOf("about:") != 0)
+        aHostSchemeData.push({ host: aEntry.URI.host, scheme: aEntry.URI.scheme });
+    }
+    catch (ex) {
+      // We just won't attempt to get cookies for this entry.
+    }
+
+    if (aEntry.title && aEntry.title != entry.url) {
+      entry.title = aEntry.title;
+    }
+    if (aEntry.isSubFrame) {
+      entry.subframe = true;
+    }
+    if (!(aEntry instanceof Ci.nsISHEntry)) {
+      return entry;
+    }
+
+    var cacheKey = aEntry.cacheKey;
+    if (cacheKey && cacheKey instanceof Ci.nsISupportsPRUint32 &&
+        cacheKey.data != 0) {
+      // XXXbz would be better to have cache keys implement
+      // nsISerializable or something.
+      entry.cacheKey = cacheKey.data;
+    }
+    entry.ID = aEntry.ID;
+    entry.docshellID = aEntry.docshellID;
+
+    if (aEntry.referrerURI)
+      entry.referrer = aEntry.referrerURI.spec;
+
+    if (aEntry.srcdocData)
+      entry.srcdocData = aEntry.srcdocData;
+
+    if (aEntry.isSrcdocEntry)
+      entry.isSrcdocEntry = aEntry.isSrcdocEntry;
+
+    if (aEntry.contentType)
+      entry.contentType = aEntry.contentType;
+
+    var x = {}, y = {};
+    aEntry.getScrollPosition(x, y);
+    if (x.value != 0 || y.value != 0)
+      entry.scroll = x.value + "," + y.value;
+
+    try {
+      var prefPostdata = this._prefBranch.getIntPref("sessionstore.postdata");
+      if (aEntry.postData && (aFullData || prefPostdata &&
+            this.checkPrivacyLevel(aEntry.URI.schemeIs("https"), aIsPinned))) {
+        aEntry.postData.QueryInterface(Ci.nsISeekableStream).
+                        seek(Ci.nsISeekableStream.NS_SEEK_SET, 0);
+        var stream = Cc["@mozilla.org/binaryinputstream;1"].
+                     createInstance(Ci.nsIBinaryInputStream);
+        stream.setInputStream(aEntry.postData);
+        var postBytes = stream.readByteArray(stream.available());
+        var postdata = String.fromCharCode.apply(null, postBytes);
+        if (aFullData || prefPostdata == -1 ||
+            postdata.replace(/^(Content-.*\r\n)+(\r\n)*/, "").length <=
+              prefPostdata) {
+          // We can stop doing base64 encoding once our serialization into JSON
+          // is guaranteed to handle all chars in strings, including embedded
+          // nulls.
+          entry.postdata_b64 = btoa(postdata);
+        }
+      }
+    }
+    catch (ex) { debug(ex); } // POSTDATA is tricky - especially since some extensions don't get it right
+
+    if (aEntry.triggeringPrincipal) {
+      // Not catching anything specific here, just possible errors
+      // from writeCompoundObject and the like.
+      try {
+        var binaryStream = Cc["@mozilla.org/binaryoutputstream;1"].
+                           createInstance(Ci.nsIObjectOutputStream);
+        var pipe = Cc["@mozilla.org/pipe;1"].createInstance(Ci.nsIPipe);
+        pipe.init(false, false, 0, 0xffffffff, null);
+        binaryStream.setOutputStream(pipe.outputStream);
+        binaryStream.writeCompoundObject(aEntry.triggeringPrincipal, Ci.nsIPrincipal, true);
+        binaryStream.close();
+
+        // Now we want to read the data from the pipe's input end and encode it.
+        var scriptableStream = Cc["@mozilla.org/binaryinputstream;1"].
+                               createInstance(Ci.nsIBinaryInputStream);
+        scriptableStream.setInputStream(pipe.inputStream);
+        var triggeringPrincipalBytes =
+          scriptableStream.readByteArray(scriptableStream.available());
+        // We can stop doing base64 encoding once our serialization into JSON
+        // is guaranteed to handle all chars in strings, including embedded
+        // nulls.
+        entry.triggeringPrincipal_b64 = btoa(String.fromCharCode.apply(null, triggeringPrincipalBytes));
+      }
+      catch (ex) { debug(ex); }
+    }
+
+    entry.docIdentifier = aEntry.BFCacheEntry.ID;
+
+    if (aEntry.stateData != null) {
+      entry.structuredCloneState = aEntry.stateData.getDataAsBase64();
+      entry.structuredCloneVersion = aEntry.stateData.formatVersion;
+    }
+
+    if (!(aEntry instanceof Ci.nsISHContainer)) {
+      return entry;
+    }
+
+    if (aEntry.childCount > 0) {
+      let children = [];
+      for (var i = 0; i < aEntry.childCount; i++) {
+        var child = aEntry.GetChildAt(i);
+
+        if (child) {
+          // don't try to restore framesets containing wyciwyg URLs (cf. bug 424689 and bug 450595)
+          if (child.URI.schemeIs("wyciwyg")) {
+            children = [];
+            break;
+          }
+
+          children.push(this._serializeHistoryEntry(child, aFullData,
+                                                    aIsPinned, aHostSchemeData));
+        }
+      }
+
+      if (children.length)
+        entry.children = children;
+    }
+
+    return entry;
+  },
+
+  /**
+   * go through all tabs and store the current scroll positions
+   * and innerHTML content of WYSIWYG editors
+   * @param aWindow
+   *        Window reference
+   */
+  _updateTextAndScrollData: function ssi_updateTextAndScrollData(aWindow) {
+    var browsers = aWindow.gBrowser.browsers;
+    this._windows[aWindow.__SSi].tabs.forEach(function (tabData, i) {
+      try {
+        this._updateTextAndScrollDataForTab(aWindow, browsers[i], tabData);
+      }
+      catch (ex) { debug(ex); } // get as much data as possible, ignore failures (might succeed the next time)
+    }, this);
+  },
+
+  /**
+   * go through all frames and store the current scroll positions
+   * and innerHTML content of WYSIWYG editors
+   * @param aWindow
+   *        Window reference
+   * @param aBrowser
+   *        single browser reference
+   * @param aTabData
+   *        tabData object to add the information to
+   * @param aFullData
+   *        always return privacy sensitive data (use with care)
+   */
+  _updateTextAndScrollDataForTab:
+    function ssi_updateTextAndScrollDataForTab(aWindow, aBrowser, aTabData, aFullData) {
+    // we shouldn't update data for incompletely initialized tabs
+    if (aBrowser.__SS_data && aBrowser.__SS_tabStillLoading)
+      return;
+
+    var tabIndex = (aTabData.index || aTabData.entries.length) - 1;
+    // entry data needn't exist for tabs just initialized with an incomplete session state
+    if (!aTabData.entries[tabIndex])
+      return;
+
+    let selectedPageStyle = aBrowser.markupDocumentViewer.authorStyleDisabled ? "_nostyle" :
+                            this._getSelectedPageStyle(aBrowser.contentWindow);
+    if (selectedPageStyle)
+      aTabData.pageStyle = selectedPageStyle;
+    else if (aTabData.pageStyle)
+      delete aTabData.pageStyle;
+
+    this._updateTextAndScrollDataForFrame(aWindow, aBrowser.contentWindow,
+                                          aTabData.entries[tabIndex],
+                                          !aBrowser.__SS_formDataSaved, aFullData,
+                                          !!aTabData.pinned);
+    aBrowser.__SS_formDataSaved = true;
+    if (aBrowser.currentURI.spec == "about:config")
+      aTabData.entries[tabIndex].formdata = {
+        id: {
+          "textbox": aBrowser.contentDocument.getElementById("textbox").value
+        },
+        xpath: {}
+      };
+  },
+
+  /**
+   * go through all subframes and store all form data, the current
+   * scroll positions and innerHTML content of WYSIWYG editors
+   * @param aWindow
+   *        Window reference
+   * @param aContent
+   *        frame reference
+   * @param aData
+   *        part of a tabData object to add the information to
+   * @param aUpdateFormData
+   *        update all form data for this tab
+   * @param aFullData
+   *        always return privacy sensitive data (use with care)
+   * @param aIsPinned
+   *        the tab is pinned and should be treated differently for privacy
+   */
+  _updateTextAndScrollDataForFrame:
+    function ssi_updateTextAndScrollDataForFrame(aWindow, aContent, aData,
+                                                 aUpdateFormData, aFullData, aIsPinned) {
+    for (var i = 0; i < aContent.frames.length; i++) {
+      if (aData.children && aData.children[i])
+        this._updateTextAndScrollDataForFrame(aWindow, aContent.frames[i],
+                                              aData.children[i], aUpdateFormData,
+                                              aFullData, aIsPinned);
+    }
+    var isHTTPS = this._getURIFromString((aContent.parent || aContent).
+                                         document.location.href).schemeIs("https");
+    let isAboutSR = aContent.top.document.location.href == "about:sessionrestore";
+    if (aFullData || this.checkPrivacyLevel(isHTTPS, aIsPinned) || isAboutSR) {
+      if (aFullData || aUpdateFormData) {
+        let formData = DocumentUtils.getFormData(aContent.document);
+
+        // We want to avoid saving data for about:sessionrestore as a string.
+        // Since it's stored in the form as stringified JSON, stringifying further
+        // causes an explosion of escape characters. cf. bug 467409
+        if (formData && isAboutSR) {
+          formData.id["sessionData"] = JSON.parse(formData.id["sessionData"]);
+        }
+
+        if (Object.keys(formData.id).length ||
+            Object.keys(formData.xpath).length) {
+          aData.formdata = formData;
+        } else if (aData.formdata) {
+          delete aData.formdata;
+        }
+      }
+
+      // designMode is undefined e.g. for XUL documents (as about:config)
+      if ((aContent.document.designMode || "") == "on" && aContent.document.body)
+        aData.innerHTML = aContent.document.body.innerHTML;
+    }
+
+    // get scroll position from nsIDOMWindowUtils, since it allows avoiding a
+    // flush of layout
+    let domWindowUtils = aContent.QueryInterface(Ci.nsIInterfaceRequestor)
+                                 .getInterface(Ci.nsIDOMWindowUtils);
+    let scrollX = {}, scrollY = {};
+    domWindowUtils.getScrollXY(false, scrollX, scrollY);
+    aData.scroll = scrollX.value + "," + scrollY.value;
+  },
+
+  /**
+   * determine the title of the currently enabled style sheet (if any)
+   * and recurse through the frameset if necessary
+   * @param   aContent is a frame reference
+   * @returns the title style sheet determined to be enabled (empty string if none)
+   */
+  _getSelectedPageStyle: function ssi_getSelectedPageStyle(aContent) {
+    const forScreen = /(?:^|,)\s*(?:all|screen)\s*(?:,|$)/i;
+    for (let i = 0; i < aContent.document.styleSheets.length; i++) {
+      let ss = aContent.document.styleSheets[i];
+      let media = ss.media.mediaText;
+      if (!ss.disabled && ss.title && (!media || forScreen.test(media)))
+        return ss.title
+    }
+    for (let i = 0; i < aContent.frames.length; i++) {
+      let selectedPageStyle = this._getSelectedPageStyle(aContent.frames[i]);
+      if (selectedPageStyle)
+        return selectedPageStyle;
+    }
+    return "";
+  },
+
+  /**
+   * extract the base domain from a history entry and its children
+   * @param aEntry
+   *        the history entry, serialized
+   * @param aHosts
+   *        the hash that will be used to store hosts eg, { hostname: true }
+   * @param aCheckPrivacy
+   *        should we check the privacy level for https
+   * @param aIsPinned
+   *        is the entry we're evaluating for a pinned tab; used only if
+   *        aCheckPrivacy
+   */
+  _extractHostsForCookiesFromEntry:
+    function ssi_extractHostsForCookiesFromEntry(aEntry, aHosts, aCheckPrivacy, aIsPinned) {
+
+    let host = aEntry._host,
+        scheme = aEntry._scheme;
+
+    // If host & scheme aren't defined, then we are likely here in the startup
+    // process via _splitCookiesFromWindow. In that case, we'll turn aEntry.url
+    // into an nsIURI and get host/scheme from that. This will throw for about:
+    // urls in which case we don't need to do anything.
+    if (!host && !scheme) {
+      try {
+        let uri = this._getURIFromString(aEntry.url);
+        host = uri.host;
+        scheme = uri.scheme;
+        this._extractHostsForCookiesFromHostScheme(host, scheme, aHosts, aCheckPrivacy, aIsPinned);
+      }
+      catch(ex) { }
+    }
+
+    if (aEntry.children) {
+      aEntry.children.forEach(function(entry) {
+        this._extractHostsForCookiesFromEntry(entry, aHosts, aCheckPrivacy, aIsPinned);
+      }, this);
+    }
+  },
+
+  /**
+   * extract the base domain from a host & scheme
+   * @param aHost
+   *        the host of a uri (usually via nsIURI.host)
+   * @param aScheme
+   *        the scheme of a uri (usually via nsIURI.scheme)
+   * @param aHosts
+   *        the hash that will be used to store hosts eg, { hostname: true }
+   * @param aCheckPrivacy
+   *        should we check the privacy level for https
+   * @param aIsPinned
+   *        is the entry we're evaluating for a pinned tab; used only if
+   *        aCheckPrivacy
+   */
+  _extractHostsForCookiesFromHostScheme:
+    function ssi_extractHostsForCookiesFromHostScheme(aHost, aScheme, aHosts, aCheckPrivacy, aIsPinned) {
+    // host and scheme may not be set (for about: urls for example), in which
+    // case testing scheme will be sufficient.
+    if (/https?/.test(aScheme) && !aHosts[aHost] &&
+        (!aCheckPrivacy ||
+         this.checkPrivacyLevel(aScheme == "https", aIsPinned))) {
+      // By setting this to true or false, we can determine when looking at
+      // the host in _updateCookies if we should check for privacy.
+      aHosts[aHost] = aIsPinned;
+    }
+    else if (aScheme == "file") {
+      aHosts[aHost] = true;
+    }
+  },
+
+  /**
+   * store all hosts for a URL
+   * @param aWindow
+   *        Window reference
+   */
+  _updateCookieHosts: function ssi_updateCookieHosts(aWindow) {
+    var hosts = this._internalWindows[aWindow.__SSi].hosts = {};
+
+    // Since _updateCookiesHosts is only ever called for open windows during a
+    // session, we can call into _extractHostsForCookiesFromHostScheme directly
+    // using data that is attached to each browser.
+    for (let i = 0; i < aWindow.gBrowser.tabs.length; i++) {
+      let tab = aWindow.gBrowser.tabs[i];
+      let hostSchemeData = tab.linkedBrowser.__SS_hostSchemeData || [];
+      for (let j = 0; j < hostSchemeData.length; j++) {
+        this._extractHostsForCookiesFromHostScheme(hostSchemeData[j].host,
+                                                   hostSchemeData[j].scheme,
+                                                   hosts, true, tab.pinned);
+      }
+    }
+  },
+
+  /**
+   * Serialize cookie data
+   * @param aWindows
+   *        JS object containing window data references
+   *        { id: winData, etc. }
+   */
+  _updateCookies: function ssi_updateCookies(aWindows) {
+    function addCookieToHash(aHash, aHost, aPath, aName, aCookie) {
+      // lazily build up a 3-dimensional hash, with
+      // aHost, aPath, and aName as keys
+      if (!aHash[aHost])
+        aHash[aHost] = {};
+      if (!aHash[aHost][aPath])
+        aHash[aHost][aPath] = {};
+      aHash[aHost][aPath][aName] = aCookie;
+    }
+
+    var jscookies = {};
+    var _this = this;
+    // MAX_EXPIRY should be 2^63-1, but JavaScript can't handle that precision
+    var MAX_EXPIRY = Math.pow(2, 62);
+
+    for (let [id, window] in Iterator(aWindows)) {
+      window.cookies = [];
+      let internalWindow = this._internalWindows[id];
+      if (!internalWindow.hosts)
+        return;
+      for (var [host, isPinned] in Iterator(internalWindow.hosts)) {
+        let list;
+        try {
+          list = Services.cookies.getCookiesFromHost(host, {});
+        }
+        catch (ex) {
+          debug("getCookiesFromHost failed. Host: " + host);
+        }
+        while (list && list.hasMoreElements()) {
+          var cookie = list.getNext().QueryInterface(Ci.nsICookie2);
+          // window._hosts will only have hosts with the right privacy rules,
+          // so there is no need to do anything special with this call to
+          // checkPrivacyLevel.
+          if (cookie.isSession && _this.checkPrivacyLevel(cookie.isSecure, isPinned)) {
+            // use the cookie's host, path, and name as keys into a hash,
+            // to make sure we serialize each cookie only once
+            if (!(cookie.host in jscookies &&
+                  cookie.path in jscookies[cookie.host] &&
+                  cookie.name in jscookies[cookie.host][cookie.path])) {
+              var jscookie = { "host": cookie.host, "value": cookie.value };
+              // only add attributes with non-default values (saving a few bits)
+              if (cookie.path) jscookie.path = cookie.path;
+              if (cookie.name) jscookie.name = cookie.name;
+              if (cookie.isSecure) jscookie.secure = true;
+              if (cookie.isHttpOnly) jscookie.httponly = true;
+              if (cookie.expiry < MAX_EXPIRY) jscookie.expiry = cookie.expiry;
+
+              addCookieToHash(jscookies, cookie.host, cookie.path, cookie.name, jscookie);
+            }
+            window.cookies.push(jscookies[cookie.host][cookie.path][cookie.name]);
+          }
+        }
+      }
+
+      // don't include empty cookie sections
+      if (!window.cookies.length)
+        delete window.cookies;
+    }
+  },
+
+  /**
+   * Store window dimensions, visibility, sidebar
+   * @param aWindow
+   *        Window reference
+   */
+  _updateWindowFeatures: function ssi_updateWindowFeatures(aWindow) {
+    var winData = this._windows[aWindow.__SSi];
+
+    WINDOW_ATTRIBUTES.forEach(function(aAttr) {
+      winData[aAttr] = this._getWindowDimension(aWindow, aAttr);
+    }, this);
+
+    var hidden = WINDOW_HIDEABLE_FEATURES.filter(function(aItem) {
+      return aWindow[aItem] && !aWindow[aItem].visible;
+    });
+    if (hidden.length != 0)
+      winData.hidden = hidden.join(",");
+    else if (winData.hidden)
+      delete winData.hidden;
+
+    var sidebar = aWindow.document.getElementById("sidebar-box").getAttribute("sidebarcommand");
+    if (sidebar)
+      winData.sidebar = sidebar;
+    else if (winData.sidebar)
+      delete winData.sidebar;
+  },
+
+  /**
+   * gather session data as object
+   * @param aUpdateAll
+   *        Bool update all windows
+   * @param aPinnedOnly
+   *        Bool collect pinned tabs only
+   * @returns object
+   */
+  _getCurrentState: function ssi_getCurrentState(aUpdateAll, aPinnedOnly) {
+    this._handleClosedWindows();
+
+    var activeWindow = this._getMostRecentBrowserWindow();
+
+    if (this._loadState == STATE_RUNNING) {
+      // update the data for all windows with activities since the last save operation
+      this._forEachBrowserWindow(function(aWindow) {
+        if (!this._isWindowLoaded(aWindow)) // window data is still in _statesToRestore
+          return;
+        if (aUpdateAll || this._dirtyWindows[aWindow.__SSi] || aWindow == activeWindow) {
+          this._collectWindowData(aWindow);
+        }
+        else { // always update the window features (whose change alone never triggers a save operation)
+          this._updateWindowFeatures(aWindow);
+        }
+      });
+      this._dirtyWindows = [];
+    }
+
+    // collect the data for all windows
+    var total = [], windows = {}, ids = [];
+    var nonPopupCount = 0;
+    var ix;
+    for (ix in this._windows) {
+      if (this._windows[ix]._restoring) // window data is still in _statesToRestore
+        continue;
+      total.push(this._windows[ix]);
+      ids.push(ix);
+      windows[ix] = this._windows[ix];
+      if (!this._windows[ix].isPopup)
+        nonPopupCount++;
+    }
+    this._updateCookies(windows);
+
+    // collect the data for all windows yet to be restored
+    for (ix in this._statesToRestore) {
+      for each (let winData in this._statesToRestore[ix].windows) {
+        total.push(winData);
+        if (!winData.isPopup)
+          nonPopupCount++;
+      }
+    }
+
+    // shallow copy this._closedWindows to preserve current state
+    let lastClosedWindowsCopy = this._closedWindows.slice();
+
+#ifndef XP_MACOSX
+    // If no non-popup browser window remains open, return the state of the last
+    // closed window(s). We only want to do this when we're actually "ending"
+    // the session.
+    //XXXzpao We should do this for _restoreLastWindow == true, but that has
+    //        its own check for popups. c.f. bug 597619
+    if (nonPopupCount == 0 && lastClosedWindowsCopy.length > 0 &&
+        this._loadState == STATE_QUITTING) {
+      // prepend the last non-popup browser window, so that if the user loads more tabs
+      // at startup we don't accidentally add them to a popup window
+      do {
+        total.unshift(lastClosedWindowsCopy.shift())
+      } while (total[0].isPopup && lastClosedWindowsCopy.length > 0)
+    }
+#endif
+
+    if (aPinnedOnly) {
+      // perform a deep copy so that existing session variables are not changed.
+      total = JSON.parse(this._toJSONString(total));
+      total = total.filter(function (win) {
+        win.tabs = win.tabs.filter(function (tab) tab.pinned);
+        // remove closed tabs
+        win._closedTabs = [];
+        // correct selected tab index if it was stripped out
+        if (win.selected > win.tabs.length)
+          win.selected = 1;
+        return win.tabs.length > 0;
+      });
+      if (total.length == 0)
+        return null;
+
+      lastClosedWindowsCopy = [];
+    }
+
+    if (activeWindow) {
+      this.activeWindowSSiCache = activeWindow.__SSi || "";
+    }
+    ix = ids.indexOf(this.activeWindowSSiCache);
+    // We don't want to restore focus to a minimized window or a window which had all its
+    // tabs stripped out (doesn't exist).
+    if (ix != -1 && total[ix] && total[ix].sizemode == "minimized")
+      ix = -1;
+
+    let session = {
+      state: this._loadState == STATE_RUNNING ? STATE_RUNNING_STR : STATE_STOPPED_STR,
+      lastUpdate: Date.now(),
+      startTime: this._sessionStartTime,
+      recentCrashes: this._recentCrashes
+    };
+
+    var scratchpads = null;
+    var browserConsole = null;
+#ifdef MOZ_DEVTOOLS
+    // Scratchpad
+    // get open Scratchpad window states too
+    scratchpads = ScratchpadManager.getSessionState();
+
+    // The Browser Console
+    browserConsole = HUDService.getBrowserConsoleSessionState();
+#endif
+
+    return {
+      windows: total,
+      selectedWindow: ix + 1,
+      _closedWindows: lastClosedWindowsCopy,
+#ifdef MOZ_DEVTOOLS
+      session: session,
+      scratchpads: scratchpads,
+      browserConsole: browserConsole
+#else
+      session: session
+#endif
+    };
+  },
+
+  /**
+   * serialize session data for a window
+   * @param aWindow
+   *        Window reference
+   * @returns string
+   */
+  _getWindowState: function ssi_getWindowState(aWindow) {
+    if (!this._isWindowLoaded(aWindow))
+      return this._statesToRestore[aWindow.__SS_restoreID];
+
+    if (this._loadState == STATE_RUNNING) {
+      this._collectWindowData(aWindow);
+    }
+
+    var winData = this._windows[aWindow.__SSi];
+    let windows = {};
+    windows[aWindow.__SSi] = winData;
+    this._updateCookies(windows);
+
+    return { windows: [winData] };
+  },
+
+  _collectWindowData: function ssi_collectWindowData(aWindow) {
+    if (!this._isWindowLoaded(aWindow))
+      return;
+
+    // update the internal state data for this window
+    this._saveWindowHistory(aWindow);
+    this._updateTextAndScrollData(aWindow);
+    this._updateCookieHosts(aWindow);
+    this._updateWindowFeatures(aWindow);
+
+    // Make sure we keep __SS_lastSessionWindowID around for cases like entering
+    // or leaving PB mode.
+    if (aWindow.__SS_lastSessionWindowID)
+      this._windows[aWindow.__SSi].__lastSessionWindowID =
+        aWindow.__SS_lastSessionWindowID;
+
+    this._dirtyWindows[aWindow.__SSi] = false;
+  },
+
+  /* ........ Restoring Functionality .............. */
+
+  /**
+   * restore features to a single window
+   * @param aWindow
+   *        Window reference
+   * @param aState
+   *        JS object or its eval'able source
+   * @param aOverwriteTabs
+   *        bool overwrite existing tabs w/ new ones
+   * @param aFollowUp
+   *        bool this isn't the restoration of the first window
+   */
+  restoreWindow: function ssi_restoreWindow(aWindow, aState, aOverwriteTabs, aFollowUp) {
+    if (!aFollowUp) {
+      this.windowToFocus = aWindow;
+    }
+    // initialize window if necessary
+    if (aWindow && (!aWindow.__SSi || !this._windows[aWindow.__SSi]))
+      this.onLoad(aWindow);
+
+    try {
+      var root = typeof aState == "string" ? JSON.parse(aState) : aState;
+      if (!root.windows[0]) {
+        this._sendRestoreCompletedNotifications();
+        return; // nothing to restore
+      }
+    }
+    catch (ex) { // invalid state object - don't restore anything
+      debug(ex);
+      this._sendRestoreCompletedNotifications();
+      return;
+    }
+
+    // We're not returning from this before we end up calling restoreHistoryPrecursor
+    // for this window, so make sure we send the SSWindowStateBusy event.
+    this._setWindowStateBusy(aWindow);
+
+    if (root._closedWindows)
+      this._closedWindows = root._closedWindows;
+
+    var winData;
+    if (!root.selectedWindow || root.selectedWindow > root.windows.length) {
+      root.selectedWindow = 0;
+    }
+
+    // open new windows for all further window entries of a multi-window session
+    // (unless they don't contain any tab data)
+    for (var w = 1; w < root.windows.length; w++) {
+      winData = root.windows[w];
+      if (winData && winData.tabs && winData.tabs[0]) {
+        var window = this._openWindowWithState({ windows: [winData] });
+        if (w == root.selectedWindow - 1) {
+          this.windowToFocus = window;
+        }
+      }
+    }
+    winData = root.windows[0];
+    if (!winData.tabs) {
+      winData.tabs = [];
+    }
+    // don't restore a single blank tab when we've had an external
+    // URL passed in for loading at startup (cf. bug 357419)
+    else if (root._firstTabs && !aOverwriteTabs && winData.tabs.length == 1 &&
+             (!winData.tabs[0].entries || winData.tabs[0].entries.length == 0)) {
+      winData.tabs = [];
+    }
+
+    var tabbrowser = aWindow.gBrowser;
+    var openTabCount = aOverwriteTabs ? tabbrowser.browsers.length : -1;
+    var newTabCount = winData.tabs.length;
+    var tabs = [];
+
+    // disable smooth scrolling while adding, moving, removing and selecting tabs
+    var tabstrip = tabbrowser.tabContainer.mTabstrip;
+    var smoothScroll = tabstrip.smoothScroll;
+    tabstrip.smoothScroll = false;
+
+    // unpin all tabs to ensure they are not reordered in the next loop
+    if (aOverwriteTabs) {
+      for (let t = tabbrowser._numPinnedTabs - 1; t > -1; t--)
+        tabbrowser.unpinTab(tabbrowser.tabs[t]);
+    }
+
+    // make sure that the selected tab won't be closed in order to
+    // prevent unnecessary flickering
+    if (aOverwriteTabs && tabbrowser.selectedTab._tPos >= newTabCount)
+      tabbrowser.moveTabTo(tabbrowser.selectedTab, newTabCount - 1);
+
+    let numVisibleTabs = 0;
+
+    for (var t = 0; t < newTabCount; t++) {
+      tabs.push(t < openTabCount ?
+                tabbrowser.tabs[t] :
+                tabbrowser.addTab("about:blank",
+                                  {skipAnimation: true,
+                                   skipBackgroundNotify: true}));
+      // when resuming at startup: add additionally requested pages to the end
+      if (!aOverwriteTabs && root._firstTabs) {
+        tabbrowser.moveTabTo(tabs[t], t);
+      }
+
+      if (winData.tabs[t].pinned)
+        tabbrowser.pinTab(tabs[t]);
+
+      if (winData.tabs[t].hidden) {
+        tabbrowser.hideTab(tabs[t]);
+      }
+      else {
+        tabbrowser.showTab(tabs[t]);
+        numVisibleTabs++;
+      }
+    }
+
+    // if all tabs to be restored are hidden, make the first one visible
+    if (!numVisibleTabs && winData.tabs.length) {
+      winData.tabs[0].hidden = false;
+      tabbrowser.showTab(tabs[0]);
+    }
+
+    // If overwriting tabs, we want to reset each tab's "restoring" state. Since
+    // we're overwriting those tabs, they should no longer be restoring. The
+    // tabs will be rebuilt and marked if they need to be restored after loading
+    // state (in restoreHistoryPrecursor).
+    if (aOverwriteTabs) {
+      for (let i = 0; i < tabbrowser.tabs.length; i++) {
+        if (tabbrowser.browsers[i].__SS_restoreState)
+          this._resetTabRestoringState(tabbrowser.tabs[i]);
+      }
+    }
+
+    // We want to set up a counter on the window that indicates how many tabs
+    // in this window are unrestored. This will be used in restoreNextTab to
+    // determine if gRestoreTabsProgressListener should be removed from the window.
+    // If we aren't overwriting existing tabs, then we want to add to the existing
+    // count in case there are still tabs restoring.
+    if (!aWindow.__SS_tabsToRestore)
+      aWindow.__SS_tabsToRestore = 0;
+    if (aOverwriteTabs)
+      aWindow.__SS_tabsToRestore = newTabCount;
+    else
+      aWindow.__SS_tabsToRestore += newTabCount;
+
+    // We want to correlate the window with data from the last session, so
+    // assign another id if we have one. Otherwise clear so we don't do
+    // anything with it.
+    delete aWindow.__SS_lastSessionWindowID;
+    if (winData.__lastSessionWindowID)
+      aWindow.__SS_lastSessionWindowID = winData.__lastSessionWindowID;
+
+    // when overwriting tabs, remove all superflous ones
+    if (aOverwriteTabs && newTabCount < openTabCount) {
+      Array.slice(tabbrowser.tabs, newTabCount, openTabCount)
+           .forEach(tabbrowser.removeTab, tabbrowser);
+    }
+
+    if (aOverwriteTabs) {
+      this.restoreWindowFeatures(aWindow, winData);
+      delete this._windows[aWindow.__SSi].extData;
+    }
+    if (winData.cookies) {
+      this.restoreCookies(winData.cookies);
+    }
+    if (winData.extData) {
+      if (!this._windows[aWindow.__SSi].extData) {
+        this._windows[aWindow.__SSi].extData = {};
+      }
+      for (var key in winData.extData) {
+        this._windows[aWindow.__SSi].extData[key] = winData.extData[key];
+      }
+    }
+    if (aOverwriteTabs || root._firstTabs) {
+      this._windows[aWindow.__SSi]._closedTabs = winData._closedTabs || [];
+    }
+
+    this.restoreHistoryPrecursor(aWindow, tabs, winData.tabs,
+      (aOverwriteTabs ? (parseInt(winData.selected) || 1) : 0), 0, 0);
+
+#ifdef MOZ_DEVTOOLS
+    if (aState.scratchpads) {
+      ScratchpadManager.restoreSession(aState.scratchpads);
+    }
+
+    // The Browser Console
+    if (aState.browserConsole) {
+      HUDService.restoreBrowserConsoleSession();
+    }
+
+#endif
+    // set smoothScroll back to the original value
+    tabstrip.smoothScroll = smoothScroll;
+
+    this._sendRestoreCompletedNotifications();
+  },
+
+  /**
+   * Sets the tabs restoring order with the following priority:
+   * Selected tab, pinned tabs, optimized visible tabs, other visible tabs and
+   * hidden tabs.
+   * @param aTabBrowser
+   *        Tab browser object
+   * @param aTabs
+   *        Array of tab references
+   * @param aTabData
+   *        Array of tab data
+   * @param aSelectedTab
+   *        Index of selected tab (1 is first tab, 0 no selected tab)
+   */
+  _setTabsRestoringOrder : function ssi__setTabsRestoringOrder(
+    aTabBrowser, aTabs, aTabData, aSelectedTab) {
+
+    // Store the selected tab. Need to substract one to get the index in aTabs.
+    let selectedTab;
+    if (aSelectedTab > 0 && aTabs[aSelectedTab - 1]) {
+      selectedTab = aTabs[aSelectedTab - 1];
+    }
+
+    // Store the pinned tabs and hidden tabs.
+    let pinnedTabs = [];
+    let pinnedTabsData = [];
+    let hiddenTabs = [];
+    let hiddenTabsData = [];
+    if (aTabs.length > 1) {
+      for (let t = aTabs.length - 1; t >= 0; t--) {
+        if (aTabData[t].pinned) {
+          pinnedTabs.unshift(aTabs.splice(t, 1)[0]);
+          pinnedTabsData.unshift(aTabData.splice(t, 1)[0]);
+        } else if (aTabData[t].hidden) {
+          hiddenTabs.unshift(aTabs.splice(t, 1)[0]);
+          hiddenTabsData.unshift(aTabData.splice(t, 1)[0]);
+        }
+      }
+    }
+
+    // Optimize the visible tabs only if there is a selected tab.
+    if (selectedTab) {
+      let selectedTabIndex = aTabs.indexOf(selectedTab);
+      if (selectedTabIndex > 0) {
+        let scrollSize = aTabBrowser.tabContainer.mTabstrip.scrollClientSize;
+        let tabWidth = aTabs[0].getBoundingClientRect().width;
+        let maxVisibleTabs = Math.ceil(scrollSize / tabWidth);
+        if (maxVisibleTabs < aTabs.length) {
+          let firstVisibleTab = 0;
+          let nonVisibleTabsCount = aTabs.length - maxVisibleTabs;
+          if (nonVisibleTabsCount >= selectedTabIndex) {
+            // Selected tab is leftmost since we scroll to it when possible.
+            firstVisibleTab = selectedTabIndex;
+          } else {
+            // Selected tab is rightmost or no more room to scroll right.
+            firstVisibleTab = nonVisibleTabsCount;
+          }
+          aTabs = aTabs.splice(firstVisibleTab, maxVisibleTabs).concat(aTabs);
+          aTabData =
+            aTabData.splice(firstVisibleTab, maxVisibleTabs).concat(aTabData);
+        }
+      }
+    }
+
+    // Merge the stored tabs in order.
+    aTabs = pinnedTabs.concat(aTabs, hiddenTabs);
+    aTabData = pinnedTabsData.concat(aTabData, hiddenTabsData);
+
+    // Load the selected tab to the first position and select it.
+    if (selectedTab) {
+      let selectedTabIndex = aTabs.indexOf(selectedTab);
+      if (selectedTabIndex > 0) {
+        aTabs = aTabs.splice(selectedTabIndex, 1).concat(aTabs);
+        aTabData = aTabData.splice(selectedTabIndex, 1).concat(aTabData);
+      }
+      aTabBrowser.selectedTab = selectedTab;
+    }
+
+    return [aTabs, aTabData];
+  },
+  
+  /**
+   * Manage history restoration for a window
+   * @param aWindow
+   *        Window to restore the tabs into
+   * @param aTabs
+   *        Array of tab references
+   * @param aTabData
+   *        Array of tab data
+   * @param aSelectTab
+   *        Index of selected tab
+   * @param aIx
+   *        Index of the next tab to check readyness for
+   * @param aCount
+   *        Counter for number of times delaying b/c browser or history aren't ready
+   * @param aRestoreImmediately
+   *        Flag to indicate whether the given set of tabs aTabs should be
+   *        restored/loaded immediately even if restore_on_demand = true
+   */
+  restoreHistoryPrecursor:
+    function ssi_restoreHistoryPrecursor(aWindow, aTabs, aTabData, aSelectTab,
+                                         aIx, aCount, aRestoreImmediately = false) {
+    var tabbrowser = aWindow.gBrowser;
+
+    // make sure that all browsers and their histories are available
+    // - if one's not, resume this check in 100ms (repeat at most 10 times)
+    for (var t = aIx; t < aTabs.length; t++) {
+      try {
+        if (!tabbrowser.getBrowserForTab(aTabs[t]).webNavigation.sessionHistory) {
+          throw new Error();
+        }
+      }
+      catch (ex) { // in case browser or history aren't ready yet
+        if (aCount < 10) {
+          var restoreHistoryFunc = function(self) {
+            self.restoreHistoryPrecursor(aWindow, aTabs, aTabData, aSelectTab,
+                                         aIx, aCount + 1, aRestoreImmediately);
+          }
+          aWindow.setTimeout(restoreHistoryFunc, 100, this);
+          return;
+        }
+      }
+    }
+
+    if (!this._isWindowLoaded(aWindow)) {
+      // from now on, the data will come from the actual window
+      delete this._statesToRestore[aWindow.__SS_restoreID];
+      delete aWindow.__SS_restoreID;
+      delete this._windows[aWindow.__SSi]._restoring;
+
+      // It's important to set the window state to dirty so that
+      // we collect their data for the first time when saving state.
+      this._dirtyWindows[aWindow.__SSi] = true;
+    }
+
+    if (aTabs.length == 0) {
+      // this is normally done in restoreHistory() but as we're returning early
+      // here we need to take care of it.
+      this._setWindowStateReady(aWindow);
+      return;
+    }
+
+    // Sets the tabs restoring order. 
+    [aTabs, aTabData] =
+      this._setTabsRestoringOrder(tabbrowser, aTabs, aTabData, aSelectTab);
+
+    // Prepare the tabs so that they can be properly restored. We'll pin/unpin
+    // and show/hide tabs as necessary. We'll also set the labels, user typed
+    // value, and attach a copy of the tab's data in case we close it before
+    // it's been restored.
+    for (t = 0; t < aTabs.length; t++) {
+      let tab = aTabs[t];
+      let browser = tabbrowser.getBrowserForTab(tab);
+      let tabData = aTabData[t];
+
+      if (tabData.pinned)
+        tabbrowser.pinTab(tab);
+      else
+        tabbrowser.unpinTab(tab);
+
+      if (tabData.hidden)
+        tabbrowser.hideTab(tab);
+      else
+        tabbrowser.showTab(tab);
+
+      if ("attributes" in tabData) {
+        // Ensure that we persist tab attributes restored from previous sessions.
+        Object.keys(tabData.attributes).forEach(a => TabAttributes.persist(a));
+      }
+
+      browser.__SS_tabStillLoading = true;
+
+      // keep the data around to prevent dataloss in case
+      // a tab gets closed before it's been properly restored
+      browser.__SS_data = tabData;
+      browser.__SS_restoreState = TAB_STATE_NEEDS_RESTORE;
+      browser.setAttribute("pending", "true");
+      tab.setAttribute("pending", "true");
+
+      // Make sure that set/getTabValue will set/read the correct data by
+      // wiping out any current value in tab.__SS_extdata.
+      delete tab.__SS_extdata;
+
+      if (!tabData.entries || tabData.entries.length == 0) {
+        // make sure to blank out this tab's content
+        // (just purging the tab's history won't be enough)
+        browser.contentDocument.location = "about:blank";
+        continue;
+      }
+
+      browser.stop(); // in case about:blank isn't done yet
+
+      // wall-paper fix for bug 439675: make sure that the URL to be loaded
+      // is always visible in the address bar
+      let activeIndex = (tabData.index || tabData.entries.length) - 1;
+      let activePageData = tabData.entries[activeIndex] || null;
+      let uri = activePageData ? activePageData.url || null : null;
+      browser.userTypedValue = uri;
+
+      // Also make sure currentURI is set so that switch-to-tab works before
+      // the tab is restored. We'll reset this to about:blank when we try to
+      // restore the tab to ensure that docshell doeesn't get confused.
+      if (uri)
+        browser.docShell.setCurrentURI(this._getURIFromString(uri));
+
+      // If the page has a title, set it.
+      if (activePageData) {
+        if (activePageData.title) {
+          tab.label = activePageData.title;
+          tab.crop = "end";
+        } else if (activePageData.url != "about:blank") {
+          tab.label = activePageData.url;
+          tab.crop = "center";
+        }
+      }
+    }
+
+    // helper hashes for ensuring unique frame IDs and unique document
+    // identifiers.
+    var idMap = { used: {} };
+    var docIdentMap = {};
+    this.restoreHistory(aWindow, aTabs, aTabData, idMap, docIdentMap,
+                        aRestoreImmediately);
+  },
+
+  /**
+   * Restore history for a window
+   * @param aWindow
+   *        Window reference
+   * @param aTabs
+   *        Array of tab references
+   * @param aTabData
+   *        Array of tab data
+   * @param aIdMap
+   *        Hash for ensuring unique frame IDs
+   * @param aRestoreImmediately
+   *        Flag to indicate whether the given set of tabs aTabs should be
+   *        restored/loaded immediately even if restore_on_demand = true
+   */
+  restoreHistory:
+    function ssi_restoreHistory(aWindow, aTabs, aTabData, aIdMap, aDocIdentMap,
+                                aRestoreImmediately) {
+    var _this = this;
+    // if the tab got removed before being completely restored, then skip it
+    while (aTabs.length > 0 && !(this._canRestoreTabHistory(aTabs[0]))) {
+      aTabs.shift();
+      aTabData.shift();
+    }
+    if (aTabs.length == 0) {
+      // At this point we're essentially ready for consumers to read/write data
+      // via the sessionstore API so we'll send the SSWindowStateReady event.
+      this._setWindowStateReady(aWindow);
+      return; // no more tabs to restore
+    }
+
+    var tab = aTabs.shift();
+    var tabData = aTabData.shift();
+
+    var browser = aWindow.gBrowser.getBrowserForTab(tab);
+    var history = browser.webNavigation.sessionHistory;
+
+    if (history.count > 0) {
+      history.PurgeHistory(history.count);
+    }
+    history.QueryInterface(Ci.nsISHistoryInternal);
+
+    browser.__SS_shistoryListener = new SessionStoreSHistoryListener(tab);
+    history.addSHistoryListener(browser.__SS_shistoryListener);
+
+    if (!tabData.entries) {
+      tabData.entries = [];
+    }
+    if (tabData.extData) {
+      tab.__SS_extdata = {};
+      for (let key in tabData.extData)
+        tab.__SS_extdata[key] = tabData.extData[key];
+    }
+    else
+      delete tab.__SS_extdata;
+
+    for (var i = 0; i < tabData.entries.length; i++) {
+      //XXXzpao Wallpaper patch for bug 514751
+      if (!tabData.entries[i].url)
+        continue;
+      history.addEntry(this._deserializeHistoryEntry(tabData.entries[i],
+                                                     aIdMap, aDocIdentMap), true);
+    }
+
+    // make sure to reset the capabilities and attributes, in case this tab gets reused
+    let disallow = new Set(tabData.disallow && tabData.disallow.split(","));
+    for (let cap of gDocShellCapabilities(browser.docShell))
+      browser.docShell["allow" + cap] = !disallow.has(cap);
+
+    // Restore tab attributes.
+    if ("attributes" in tabData) {
+      TabAttributes.set(tab, tabData.attributes);
+    }
+
+    // Restore the tab icon.
+    if ("image" in tabData) {
+      // Using null as the loadingPrincipal because serializing
+      // the principal would be overkill. Within SetIcon we
+      // default to the systemPrincipal if aLoadingPrincipal is
+      // null which will allow the favicon to load.
+      aWindow.gBrowser.setIcon(tab, tabData.image, null);
+    }
+
+    if (tabData.storage && browser.docShell instanceof Ci.nsIDocShell)
+      SessionStorage.deserialize(browser.docShell, tabData.storage);
+
+    // notify the tabbrowser that the tab chrome has been restored
+    var event = aWindow.document.createEvent("Events");
+    event.initEvent("SSTabRestoring", true, false);
+    tab.dispatchEvent(event);
+
+    // Restore the history in the next tab
+    aWindow.setTimeout(function(){
+      _this.restoreHistory(aWindow, aTabs, aTabData, aIdMap, aDocIdentMap,
+                           aRestoreImmediately);
+    }, 0);
+
+    // This could cause us to ignore max_concurrent_tabs pref a bit, but
+    // it ensures each window will have its selected tab loaded.
+    if (aRestoreImmediately || aWindow.gBrowser.selectedBrowser == browser) {
+      this.restoreTab(tab);
+    }
+    else {
+      TabRestoreQueue.add(tab);
+      this.restoreNextTab();
+    }
+  },
+
+  /**
+   * Restores the specified tab. If the tab can't be restored (eg, no history or
+   * calling gotoIndex fails), then state changes will be rolled back.
+   * This method will check if gTabsProgressListener is attached to the tab's
+   * window, ensuring that we don't get caught without one.
+   * This method removes the session history listener right before starting to
+   * attempt a load. This will prevent cases of "stuck" listeners.
+   * If this method returns false, then it is up to the caller to decide what to
+   * do. In the common case (restoreNextTab), we will want to then attempt to
+   * restore the next tab. In the other case (selecting the tab, reloading the
+   * tab), the caller doesn't actually want to do anything if no page is loaded.
+   *
+   * @param aTab
+   *        the tab to restore
+   *
+   * @returns true/false indicating whether or not a load actually happened
+   */
+  restoreTab: function ssi_restoreTab(aTab) {
+    let window = aTab.ownerDocument.defaultView;
+    let browser = aTab.linkedBrowser;
+    let tabData = browser.__SS_data;
+
+    // There are cases within where we haven't actually started a load. In that
+    // that case we'll reset state changes we made and return false to the caller
+    // can handle appropriately.
+    let didStartLoad = false;
+
+    // Make sure that the tabs progress listener is attached to this window
+    this._ensureTabsProgressListener(window);
+
+    // Make sure that this tab is removed from the priority queue.
+    TabRestoreQueue.remove(aTab);
+
+    // Increase our internal count.
+    this._tabsRestoringCount++;
+
+    // Set this tab's state to restoring
+    browser.__SS_restoreState = TAB_STATE_RESTORING;
+    browser.removeAttribute("pending");
+    aTab.removeAttribute("pending");
+
+    // Remove the history listener, since we no longer need it once we start restoring
+    this._removeSHistoryListener(aTab);
+
+    let activeIndex = (tabData.index || tabData.entries.length) - 1;
+    if (activeIndex >= tabData.entries.length)
+      activeIndex = tabData.entries.length - 1;
+    // Reset currentURI.  This creates a new session history entry with a new
+    // doc identifier, so we need to explicitly save and restore the old doc
+    // identifier (corresponding to the SHEntry at activeIndex) below.
+    browser.webNavigation.setCurrentURI(this._getURIFromString("about:blank"));
+    // Attach data that will be restored on "load" event, after tab is restored.
+    if (activeIndex > -1) {
+      // restore those aspects of the currently active documents which are not
+      // preserved in the plain history entries (mainly scroll state and text data)
+      browser.__SS_restore_data = tabData.entries[activeIndex] || {};
+      browser.__SS_restore_pageStyle = tabData.pageStyle || "";
+      browser.__SS_restore_tab = aTab;
+      didStartLoad = true;
+      try {
+        // In order to work around certain issues in session history, we need to
+        // force session history to update its internal index and call reload
+        // instead of gotoIndex. See bug 597315.
+        browser.webNavigation.sessionHistory.getEntryAtIndex(activeIndex, true);
+        browser.webNavigation.sessionHistory.reloadCurrentEntry();
+        // If the user prefers it, bypass cache and always load from the network.
+        let flags = Ci.nsIWebNavigation.LOAD_FLAGS_NONE;
+        switch (this._cacheBehavior) {
+          case 2: // hard refresh
+            flags = Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_PROXY |
+                    Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE;
+            browser.webNavigation.reload(flags);
+            break;
+          case 1: // soft refresh
+            browser.webNavigation.reload(flags);
+            break;
+          default: // 0 or other: use cache, so do nothing.
+            break;
+        }
+      }
+      catch (ex) {
+        // ignore page load errors
+        aTab.removeAttribute("busy");
+        didStartLoad = false;
+      }
+    }
+
+    // Handle userTypedValue. Setting userTypedValue seems to update gURLbar
+    // as needed. Calling loadURI will cancel form filling in restoreDocument
+    if (tabData.userTypedValue) {
+      browser.userTypedValue = tabData.userTypedValue;
+      if (tabData.userTypedClear) {
+        // Make it so that we'll enter restoreDocument on page load. We will
+        // fire SSTabRestored from there. We don't have any form data to restore
+        // so we can just set the URL to null.
+        browser.__SS_restore_data = { url: null };
+        browser.__SS_restore_tab = aTab;
+        if (didStartLoad)
+          browser.stop();
+        didStartLoad = true;
+        browser.loadURIWithFlags(tabData.userTypedValue,
+                                 Ci.nsIWebNavigation.LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP);
+      }
+    }
+
+    // If we didn't start a load, then we won't reset this tab through the usual
+    // channel (via the progress listener), so reset the tab ourselves. We will
+    // also send SSTabRestored since this tab has technically been restored.
+    if (!didStartLoad) {
+      this._sendTabRestoredNotification(aTab);
+      this._resetTabRestoringState(aTab);
+    }
+
+    return didStartLoad;
+  },
+
+  /**
+   * This _attempts_ to restore the next available tab. If the restore fails,
+   * then we will attempt the next one.
+   * There are conditions where this won't do anything:
+   *   if we're in the process of quitting
+   *   if there are no tabs to restore
+   *   if we have already reached the limit for number of tabs to restore
+   */
+  restoreNextTab: function ssi_restoreNextTab() {
+    // If we call in here while quitting, we don't actually want to do anything
+    if (this._loadState == STATE_QUITTING)
+      return;
+
+    // Don't exceed the maximum number of concurrent tab restores.
+    if (this._tabsRestoringCount >= this._maxConcurrentTabRestores)
+      return;
+
+    let tab = TabRestoreQueue.shift();
+    if (tab) {
+      let didStartLoad = this.restoreTab(tab);
+      // If we don't start a load in the restored tab (eg, no entries) then we
+      // want to attempt to restore the next tab.
+      if (!didStartLoad)
+        this.restoreNextTab();
+    }
+  },
+
+  /**
+   * expands serialized history data into a session-history-entry instance
+   * @param aEntry
+   *        Object containing serialized history data for a URL
+   * @param aIdMap
+   *        Hash for ensuring unique frame IDs
+   * @returns nsISHEntry
+   */
+  _deserializeHistoryEntry:
+    function ssi_deserializeHistoryEntry(aEntry, aIdMap, aDocIdentMap) {
+
+    var shEntry = Cc["@mozilla.org/browser/session-history-entry;1"].
+                  createInstance(Ci.nsISHEntry);
+
+    shEntry.setURI(this._getURIFromString(aEntry.url));
+    shEntry.setTitle(aEntry.title || aEntry.url);
+    if (aEntry.subframe)
+      shEntry.setIsSubFrame(aEntry.subframe || false);
+    shEntry.loadType = Ci.nsIDocShellLoadInfo.loadHistory;
+    if (aEntry.contentType)
+      shEntry.contentType = aEntry.contentType;
+    if (aEntry.referrer)
+      shEntry.referrerURI = this._getURIFromString(aEntry.referrer);
+    if (aEntry.isSrcdocEntry)
+      shEntry.srcdocData = aEntry.srcdocData;
+
+    if (aEntry.cacheKey) {
+      var cacheKey = Cc["@mozilla.org/supports-PRUint32;1"].
+                     createInstance(Ci.nsISupportsPRUint32);
+      cacheKey.data = aEntry.cacheKey;
+      shEntry.cacheKey = cacheKey;
+    }
+
+    if (aEntry.ID) {
+      // get a new unique ID for this frame (since the one from the last
+      // start might already be in use)
+      var id = aIdMap[aEntry.ID] || 0;
+      if (!id) {
+        for (id = Date.now(); id in aIdMap.used; id++);
+        aIdMap[aEntry.ID] = id;
+        aIdMap.used[id] = true;
+      }
+      shEntry.ID = id;
+    }
+
+    if (aEntry.docshellID)
+      shEntry.docshellID = aEntry.docshellID;
+
+    if (aEntry.structuredCloneState && aEntry.structuredCloneVersion) {
+      shEntry.stateData =
+        Cc["@mozilla.org/docshell/structured-clone-container;1"].
+        createInstance(Ci.nsIStructuredCloneContainer);
+
+      shEntry.stateData.initFromBase64(aEntry.structuredCloneState,
+                                       aEntry.structuredCloneVersion);
+    }
+
+    if (aEntry.scroll) {
+      var scrollPos = (aEntry.scroll || "0,0").split(",");
+      scrollPos = [parseInt(scrollPos[0]) || 0, parseInt(scrollPos[1]) || 0];
+      shEntry.setScrollPosition(scrollPos[0], scrollPos[1]);
+    }
+
+    if (aEntry.postdata_b64) {
+      var postdata = atob(aEntry.postdata_b64);
+      var stream = Cc["@mozilla.org/io/string-input-stream;1"].
+                   createInstance(Ci.nsIStringInputStream);
+      stream.setData(postdata, postdata.length);
+      shEntry.postData = stream;
+    }
+
+    let childDocIdents = {};
+    if (aEntry.docIdentifier) {
+      // If we have a serialized document identifier, try to find an SHEntry
+      // which matches that doc identifier and adopt that SHEntry's
+      // BFCacheEntry.  If we don't find a match, insert shEntry as the match
+      // for the document identifier.
+      let matchingEntry = aDocIdentMap[aEntry.docIdentifier];
+      if (!matchingEntry) {
+        matchingEntry = {shEntry: shEntry, childDocIdents: childDocIdents};
+        aDocIdentMap[aEntry.docIdentifier] = matchingEntry;
+      }
+      else {
+        shEntry.adoptBFCacheEntry(matchingEntry.shEntry);
+        childDocIdents = matchingEntry.childDocIdents;
+      }
+    }
+
+    // The field aEntry.owner_b64 got renamed to aEntry.triggeringPricipal_b64 in
+    // Bug 1286472. To remain backward compatible we still have to support that
+    // field for a few cycles before we can remove it within Bug 1289785.
+     if (aEntry.owner_b64) {
+      aEntry.triggeringPrincipal_b64 = aEntry.owner_b64;
+      delete aEntry.owner_b64;
+    }
+
+    if (aEntry.triggeringPrincipal_b64) {
+      var triggeringPrincipalInput = Cc["@mozilla.org/io/string-input-stream;1"].
+                                     createInstance(Ci.nsIStringInputStream);
+      var binaryData = atob(aEntry.triggeringPrincipal_b64);
+      triggeringPrincipalInput.setData(binaryData, binaryData.length);
+      var binaryStream = Cc["@mozilla.org/binaryinputstream;1"].
+                         createInstance(Ci.nsIObjectInputStream);
+      binaryStream.setInputStream(triggeringPrincipalInput);
+      try { // Catch possible deserialization exceptions
+        shEntry.triggeringPrincipal = binaryStream.readObject(true);
+      } catch (ex) { debug(ex); }
+    }
+
+    if (aEntry.children && shEntry instanceof Ci.nsISHContainer) {
+      for (var i = 0; i < aEntry.children.length; i++) {
+        //XXXzpao Wallpaper patch for bug 514751
+        if (!aEntry.children[i].url)
+          continue;
+
+        // We're getting sessionrestore.js files with a cycle in the
+        // doc-identifier graph, likely due to bug 698656.  (That is, we have
+        // an entry where doc identifier A is an ancestor of doc identifier B,
+        // and another entry where doc identifier B is an ancestor of A.)
+        //
+        // If we were to respect these doc identifiers, we'd create a cycle in
+        // the SHEntries themselves, which causes the docshell to loop forever
+        // when it looks for the root SHEntry.
+        //
+        // So as a hack to fix this, we restrict the scope of a doc identifier
+        // to be a node's siblings and cousins, and pass childDocIdents, not
+        // aDocIdents, to _deserializeHistoryEntry.  That is, we say that two
+        // SHEntries with the same doc identifier have the same document iff
+        // they have the same parent or their parents have the same document.
+
+        shEntry.AddChild(this._deserializeHistoryEntry(aEntry.children[i], aIdMap,
+                                                       childDocIdents), i);
+      }
+    }
+
+    return shEntry;
+  },
+
+  /**
+   * Restore properties to a loaded document
+   */
+  restoreDocument: function ssi_restoreDocument(aWindow, aBrowser, aEvent) {
+    // wait for the top frame to be loaded completely
+    if (!aEvent || !aEvent.originalTarget || !aEvent.originalTarget.defaultView ||
+        aEvent.originalTarget.defaultView != aEvent.originalTarget.defaultView.top) {
+      return;
+    }
+
+    // always call this before injecting content into a document!
+    function hasExpectedURL(aDocument, aURL)
+      !aURL || aURL.replace(/#.*/, "") == aDocument.location.href.replace(/#.*/, "");
+
+    let selectedPageStyle = aBrowser.__SS_restore_pageStyle;
+    function restoreTextDataAndScrolling(aContent, aData, aPrefix) {
+      if (aData.formdata && hasExpectedURL(aContent.document, aData.url)) {
+        let formdata = aData.formdata;
+
+        // handle backwards compatibility
+        // this is a migration from pre-firefox 15. cf. bug 742051
+        if (!("xpath" in formdata || "id" in formdata)) {
+          formdata = { xpath: {}, id: {} };
+
+          for each (let [key, value] in Iterator(aData.formdata)) {
+            if (key.charAt(0) == "#") {
+              formdata.id[key.slice(1)] = value;
+            } else {
+              formdata.xpath[key] = value;
+            }
+          }
+        }
+
+        // for about:sessionrestore we saved the field as JSON to avoid
+        // nested instances causing humongous sessionstore.js files.
+        // cf. bug 467409
+        if (aData.url == "about:sessionrestore" &&
+            "sessionData" in formdata.id &&
+            typeof formdata.id["sessionData"] == "object") {
+          formdata.id["sessionData"] =
+            JSON.stringify(formdata.id["sessionData"]);
+        }
+
+        // update the formdata
+        aData.formdata = formdata;
+        // merge the formdata
+        DocumentUtils.mergeFormData(aContent.document, formdata);
+      }
+
+      if (aData.innerHTML) {
+        aWindow.setTimeout(function() {
+          if (aContent.document.designMode == "on" &&
+              hasExpectedURL(aContent.document, aData.url) &&
+              aContent.document.body) {
+            aContent.document.body.innerHTML = aData.innerHTML;
+          }
+        }, 0);
+      }
+      var match;
+      if (aData.scroll && (match = /(\d+),(\d+)/.exec(aData.scroll)) != null) {
+        aContent.scrollTo(match[1], match[2]);
+      }
+      Array.forEach(aContent.document.styleSheets, function(aSS) {
+        aSS.disabled = aSS.title && aSS.title != selectedPageStyle;
+      });
+      for (var i = 0; i < aContent.frames.length; i++) {
+        if (aData.children && aData.children[i] &&
+          hasExpectedURL(aContent.document, aData.url)) {
+          restoreTextDataAndScrolling(aContent.frames[i], aData.children[i], aPrefix + i + "|");
+        }
+      }
+    }
+
+    // don't restore text data and scrolling state if the user has navigated
+    // away before the loading completed (except for in-page navigation)
+    if (hasExpectedURL(aEvent.originalTarget, aBrowser.__SS_restore_data.url)) {
+      var content = aEvent.originalTarget.defaultView;
+      restoreTextDataAndScrolling(content, aBrowser.__SS_restore_data, "");
+      aBrowser.markupDocumentViewer.authorStyleDisabled = selectedPageStyle == "_nostyle";
+    }
+
+    // notify the tabbrowser that this document has been completely restored
+    this._sendTabRestoredNotification(aBrowser.__SS_restore_tab);
+
+    delete aBrowser.__SS_restore_data;
+    delete aBrowser.__SS_restore_pageStyle;
+    delete aBrowser.__SS_restore_tab;
+  },
+
+  /**
+   * Restore visibility and dimension features to a window
+   * @param aWindow
+   *        Window reference
+   * @param aWinData
+   *        Object containing session data for the window
+   */
+  restoreWindowFeatures: function ssi_restoreWindowFeatures(aWindow, aWinData) {
+    var hidden = (aWinData.hidden)?aWinData.hidden.split(","):[];
+    WINDOW_HIDEABLE_FEATURES.forEach(function(aItem) {
+      aWindow[aItem].visible = hidden.indexOf(aItem) == -1;
+    });
+
+    if (aWinData.isPopup) {
+      this._windows[aWindow.__SSi].isPopup = true;
+      if (aWindow.gURLBar) {
+        aWindow.gURLBar.readOnly = true;
+        aWindow.gURLBar.setAttribute("enablehistory", "false");
+      }
+    }
+    else {
+      delete this._windows[aWindow.__SSi].isPopup;
+      if (aWindow.gURLBar) {
+        aWindow.gURLBar.readOnly = false;
+        aWindow.gURLBar.setAttribute("enablehistory", "true");
+      }
+    }
+
+    var _this = this;
+    aWindow.setTimeout(function() {
+      _this.restoreDimensions.apply(_this, [aWindow,
+        +aWinData.width || 0,
+        +aWinData.height || 0,
+        "screenX" in aWinData ? +aWinData.screenX : NaN,
+        "screenY" in aWinData ? +aWinData.screenY : NaN,
+        aWinData.sizemode || "", aWinData.sidebar || ""]);
+    }, 0);
+  },
+
+  /**
+   * Restore a window's dimensions
+   * @param aWidth
+   *        Window width
+   * @param aHeight
+   *        Window height
+   * @param aLeft
+   *        Window left
+   * @param aTop
+   *        Window top
+   * @param aSizeMode
+   *        Window size mode (eg: maximized)
+   * @param aSidebar
+   *        Sidebar command
+   */
+  restoreDimensions: function ssi_restoreDimensions(aWindow, aWidth, aHeight, aLeft, aTop, aSizeMode, aSidebar) {
+    var win = aWindow;
+    var _this = this;
+    function win_(aName) { return _this._getWindowDimension(win, aName); }
+
+    // Find available space on the screen where this window is being placed
+    let screen = gScreenManager.screenForRect(aLeft, aTop, aWidth, aHeight);
+    if (screen && !this._prefBranch.getBoolPref("sessionstore.exactPos")) {
+      let screenLeft = {}, screenTop = {}, screenWidth = {}, screenHeight = {};
+      screen.GetAvailRectDisplayPix(screenLeft, screenTop, screenWidth, screenHeight);
+
+      // Screen X/Y are based on the origin of the screen's desktop-pixel coordinate space
+      let screenLeftCss = screenLeft.value;
+      let screenTopCss = screenTop.value;
+      
+      // Convert the screen's device pixel dimensions to CSS px dimensions
+      screen.GetAvailRect(screenLeft, screenTop, screenWidth, screenHeight);
+      let cssToDevScale = screen.defaultCSSScaleFactor;
+      let screenRightCss = screenLeftCss + screenWidth.value / cssToDevScale;
+      let screenBottomCss = screenTopCss + screenHeight.value / cssToDevScale;
+      
+      // Pull the window within the screen's bounds.
+      // First, ensure the left edge is on-screen
+      if (aLeft < screenLeftCss) {
+        aLeft = screenLeftCss;
+      }
+      // Then check the resulting right edge, and reduce it if necessary.
+      let right = aLeft + aWidth;
+      if (right > screenRightCss) {
+        right = screenRightCss;
+        // See if we can move the left edge leftwards to maintain width.
+        if (aLeft > screenLeftCss) {
+          aLeft = Math.max(right - aWidth, screenLeftCss);
+        }
+      }
+      // Finally, update aWidth to account for the adjusted left and right edges.
+      aWidth = right - aLeft;
+
+      // Do the same in the vertical dimension.
+      // First, ensure the top edge is on-screen
+      if (aTop < screenTopCss) {
+        aTop = screenTopCss;
+      }
+      // Then check the resulting right edge, and reduce it if necessary.
+      let bottom = aTop + aHeight;
+      if (bottom > screenBottomCss) {
+        bottom = screenBottomCss;
+        // See if we can move the top edge upwards to maintain height.
+        if (aTop > screenTopCss) {
+          aTop = Math.max(bottom - aHeight, screenTopCss);
+        }
+      }
+      // Finally, update aHeight to account for the adjusted top and bottom edges.
+      aHeight = bottom - aTop;
+    }
+
+    // Only modify those aspects which aren't correct yet
+    if (!isNaN(aLeft) && !isNaN(aTop) && (aLeft != win_("screenX") || aTop != win_("screenY"))) {
+      aWindow.moveTo(aLeft, aTop);
+    }
+    if (aWidth && aHeight && (aWidth != win_("width") || aHeight != win_("height"))) {
+      // Don't resize the window if it's currently maximized and we would
+      // maximize it again shortly after.
+      if (aSizeMode != "maximized" || win_("sizemode") != "maximized") {
+        aWindow.resizeTo(aWidth, aHeight);
+      }
+    }
+    
+    // Restore window state
+    if (aSizeMode && win_("sizemode") != aSizeMode)
+    {
+      switch (aSizeMode)
+      {
+      case "maximized":
+        aWindow.maximize();
+        break;
+      case "minimized":
+        aWindow.minimize();
+        break;
+      case "normal":
+        aWindow.restore();
+        break;
+      }
+    }
+    var sidebar = aWindow.document.getElementById("sidebar-box");
+    if (sidebar.getAttribute("sidebarcommand") != aSidebar) {
+      aWindow.toggleSidebar(aSidebar);
+    }
+    // since resizing/moving a window brings it to the foreground,
+    // we might want to re-focus the last focused window
+    if (this.windowToFocus) {
+      this.windowToFocus.focus();
+    }
+  },
+
+  /**
+   * Restores cookies
+   * @param aCookies
+   *        Array of cookie objects
+   */
+  restoreCookies: function ssi_restoreCookies(aCookies) {
+    // MAX_EXPIRY should be 2^63-1, but JavaScript can't handle that precision
+    var MAX_EXPIRY = Math.pow(2, 62);
+    for (let i = 0; i < aCookies.length; i++) {
+      var cookie = aCookies[i];
+      try {
+        Services.cookies.add(cookie.host, cookie.path || "", cookie.name || "",
+                             cookie.value, !!cookie.secure, !!cookie.httponly, true,
+                             "expiry" in cookie ? cookie.expiry : MAX_EXPIRY, {});
+      }
+      catch (ex) { Cu.reportError(ex); } // don't let a single cookie stop recovering
+    }
+  },
+
+  /* ........ Disk Access .............. */
+
+  /**
+   * save state delayed by N ms
+   * marks window as dirty (i.e. data update can't be skipped)
+   * @param aWindow
+   *        Window reference
+   * @param aDelay
+   *        Milliseconds to delay
+   */
+  saveStateDelayed: function ssi_saveStateDelayed(aWindow, aDelay) {
+    if (aWindow) {
+      this._dirtyWindows[aWindow.__SSi] = true;
+    }
+
+    if (!this._saveTimer) {
+      // interval until the next disk operation is allowed
+      var minimalDelay = this._lastSaveTime + this._interval - Date.now();
+
+      // if we have to wait, set a timer, otherwise saveState directly
+      aDelay = Math.max(minimalDelay, aDelay || 2000);
+      if (aDelay > 0) {
+        this._saveTimer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+        this._saveTimer.init(this, aDelay, Ci.nsITimer.TYPE_ONE_SHOT);
+      }
+      else {
+        this.saveState();
+      }
+    }
+  },
+
+  /**
+   * save state to disk
+   * @param aUpdateAll
+   *        Bool update all windows
+   */
+  saveState: function ssi_saveState(aUpdateAll) {
+    // If crash recovery is disabled, we only want to resume with pinned tabs
+    // if we crash.
+    let pinnedOnly = this._loadState == STATE_RUNNING && !this._resume_from_crash;
+
+    var oState = this._getCurrentState(aUpdateAll, pinnedOnly);
+    if (!oState) {
+      return;
+    }
+
+    // Forget about private windows.
+    for (let i = oState.windows.length - 1; i >= 0; i--) {
+      if (oState.windows[i].isPrivate) {
+        oState.windows.splice(i, 1);
+        if (oState.selectedWindow >= i) {
+          oState.selectedWindow--;
+        }
+      }
+    }
+
+    for (let i = oState._closedWindows.length - 1; i >= 0; i--) {
+      if (oState._closedWindows[i].isPrivate) {
+        oState._closedWindows.splice(i, 1);
+      }
+    }
+
+#ifndef XP_MACOSX
+    // We want to restore closed windows that are marked with _shouldRestore.
+    // We're doing this here because we want to control this only when saving
+    // the file.
+    while (oState._closedWindows.length) {
+      let i = oState._closedWindows.length - 1;
+      if (oState._closedWindows[i]._shouldRestore) {
+        delete oState._closedWindows[i]._shouldRestore;
+        oState.windows.unshift(oState._closedWindows.pop());
+      }
+      else {
+        // We only need to go until we hit !needsRestore since we're going in reverse
+        break;
+      }
+    }
+#endif
+
+    if (pinnedOnly) {
+      // Save original resume_session_once preference for when quiting browser,
+      // otherwise session will be restored next time browser starts and we
+      // only want it to be restored in the case of a crash.
+      if (this._resume_session_once_on_shutdown == null) {
+        this._resume_session_once_on_shutdown =
+          this._prefBranch.getBoolPref("sessionstore.resume_session_once");
+        this._prefBranch.setBoolPref("sessionstore.resume_session_once", true);
+        // flush the preference file so preference will be saved in case of a crash
+        Services.prefs.savePrefFile(null);
+      }
+    }
+
+    // Persist the last session if we deferred restoring it
+    if (this._lastSessionState)
+      oState.lastSessionState = this._lastSessionState;
+
+    // Make sure that we keep the previous session if we started with a single
+    // private window and no non-private windows have been opened, yet.
+    if (this._deferredInitialState) {
+      oState.windows = this._deferredInitialState.windows || [];
+    }
+
+    this._saveStateObject(oState);
+  },
+
+  /**
+   * write a state object to disk
+   */
+  _saveStateObject: function ssi_saveStateObject(aStateObj) {
+    let data = this._toJSONString(aStateObj);
+
+    let stateString = this._createSupportsString(data);
+    Services.obs.notifyObservers(stateString, "sessionstore-state-write", "");
+    data = stateString.data;
+
+    // Don't touch the file if an observer has deleted all state data.
+    if (!data) {
+      return;
+    }
+
+    let promise;
+    // If "sessionstore.resume_from_crash" is true, attempt to backup the
+    // session file first, before writing to it.
+    if (this._resume_from_crash) {
+      // Note that we do not have race conditions here as _SessionFile
+      // guarantees that any I/O operation is completed before proceeding to
+      // the next I/O operation.
+      // Note backup happens only once, on initial save.
+      promise = this._backupSessionFileOnce;
+    } else {
+      promise = Promise.resolve();
+    }
+
+    // Attempt to write to the session file (potentially, depending on
+    // "sessionstore.resume_from_crash" preference, after successful backup).
+    promise = promise.then(function onSuccess() {
+      // Write (atomically) to a session file, using a tmp file.
+      return _SessionFile.write(data);
+    });
+
+    // Once the session file is successfully updated, save the time stamp of the
+    // last save and notify the observers.
+    promise = promise.then(() => {
+      this._lastSaveTime = Date.now();
+      Services.obs.notifyObservers(null, "sessionstore-state-write-complete",
+        "");
+    });
+  },
+
+  /* ........ Auxiliary Functions .............. */
+
+  // Wrap a string as a nsISupports
+  _createSupportsString: function ssi_createSupportsString(aData) {
+    let string = Cc["@mozilla.org/supports-string;1"]
+                   .createInstance(Ci.nsISupportsString);
+    string.data = aData;
+    return string;
+  },
+
+  /**
+   * call a callback for all currently opened browser windows
+   * (might miss the most recent one)
+   * @param aFunc
+   *        Callback each window is passed to
+   */
+  _forEachBrowserWindow: function ssi_forEachBrowserWindow(aFunc) {
+    var windowsEnum = Services.wm.getEnumerator("navigator:browser");
+
+    while (windowsEnum.hasMoreElements()) {
+      var window = windowsEnum.getNext();
+      if (window.__SSi && !window.closed) {
+        aFunc.call(this, window);
+      }
+    }
+  },
+
+  /**
+   * Returns most recent window
+   * @returns Window reference
+   */
+  _getMostRecentBrowserWindow: function ssi_getMostRecentBrowserWindow() {
+    var win = Services.wm.getMostRecentWindow("navigator:browser");
+    if (!win)
+      return null;
+    if (!win.closed)
+      return win;
+
+#ifdef BROKEN_WM_Z_ORDER
+    win = null;
+    var windowsEnum = Services.wm.getEnumerator("navigator:browser");
+    // this is oldest to newest, so this gets a bit ugly
+    while (windowsEnum.hasMoreElements()) {
+      let nextWin = windowsEnum.getNext();
+      if (!nextWin.closed)
+        win = nextWin;
+    }
+    return win;
+#else
+    var windowsEnum =
+      Services.wm.getZOrderDOMWindowEnumerator("navigator:browser", true);
+    while (windowsEnum.hasMoreElements()) {
+      win = windowsEnum.getNext();
+      if (!win.closed)
+        return win;
+    }
+    return null;
+#endif
+  },
+
+  /**
+   * Calls onClose for windows that are determined to be closed but aren't
+   * destroyed yet, which would otherwise cause getBrowserState and
+   * setBrowserState to treat them as open windows.
+   */
+  _handleClosedWindows: function ssi_handleClosedWindows() {
+    var windowsEnum = Services.wm.getEnumerator("navigator:browser");
+
+    while (windowsEnum.hasMoreElements()) {
+      var window = windowsEnum.getNext();
+      if (window.closed) {
+        this.onClose(window);
+      }
+    }
+  },
+
+  /**
+   * open a new browser window for a given session state
+   * called when restoring a multi-window session
+   * @param aState
+   *        Object containing session data
+   */
+  _openWindowWithState: function ssi_openWindowWithState(aState) {
+    var argString = Cc["@mozilla.org/supports-string;1"].
+                    createInstance(Ci.nsISupportsString);
+    argString.data = "";
+
+    // Build feature string
+    let features = "chrome,dialog=no,macsuppressanimation,all";
+    let winState = aState.windows[0];
+    WINDOW_ATTRIBUTES.forEach(function(aFeature) {
+      // Use !isNaN as an easy way to ignore sizemode and check for numbers
+      if (aFeature in winState && !isNaN(winState[aFeature]))
+        features += "," + aFeature + "=" + winState[aFeature];
+    });
+
+    if (winState.isPrivate) {
+      features += ",private";
+    }
+
+    var window =
+      Services.ww.openWindow(null, this._prefBranch.getCharPref("chromeURL"),
+                             "_blank", features, argString);
+
+    do {
+      var ID = "window" + Math.random();
+    } while (ID in this._statesToRestore);
+    this._statesToRestore[(window.__SS_restoreID = ID)] = aState;
+
+    return window;
+  },
+
+  /**
+   * Whether or not to resume session, if not recovering from a crash.
+   * @returns bool
+   */
+  _doResumeSession: function ssi_doResumeSession() {
+    return this._prefBranch.getIntPref("startup.page") == 3 ||
+           this._prefBranch.getBoolPref("sessionstore.resume_session_once");
+  },
+
+  /**
+   * whether the user wants to load any other page at startup
+   * (except the homepage) - needed for determining whether to overwrite the current tabs
+   * C.f.: nsBrowserContentHandler's defaultArgs implementation.
+   * @returns bool
+   */
+  _isCmdLineEmpty: function ssi_isCmdLineEmpty(aWindow, aState) {
+    var pinnedOnly = aState.windows &&
+                     aState.windows.every(function (win)
+                       win.tabs.every(function (tab) tab.pinned));
+
+    let hasFirstArgument = aWindow.arguments && aWindow.arguments[0];
+    if (!pinnedOnly) {
+      let defaultArgs = Cc["@mozilla.org/browser/clh;1"].
+                        getService(Ci.nsIBrowserHandler).defaultArgs;
+      if (aWindow.arguments &&
+          aWindow.arguments[0] &&
+          aWindow.arguments[0] == defaultArgs)
+        hasFirstArgument = false;
+    }
+
+    return !hasFirstArgument;
+  },
+
+  /**
+   * don't save sensitive data if the user doesn't want to
+   * (distinguishes between encrypted and non-encrypted sites)
+   * @param aIsHTTPS
+   *        Bool is encrypted
+   * @param aUseDefaultPref
+   *        don't do normal check for deferred
+   * @returns bool
+   */
+  checkPrivacyLevel: function ssi_checkPrivacyLevel(aIsHTTPS, aUseDefaultPref) {
+    let pref = "sessionstore.privacy_level";
+    // If we're in the process of quitting and we're not autoresuming the session
+    // then we should treat it as a deferred session. We have a different privacy
+    // pref for that case.
+    if (!aUseDefaultPref && this._loadState == STATE_QUITTING && !this._doResumeSession())
+      pref = "sessionstore.privacy_level_deferred";
+    return this._prefBranch.getIntPref(pref) < (aIsHTTPS ? PRIVACY_ENCRYPTED : PRIVACY_FULL);
+  },
+
+  /**
+   * on popup windows, the XULWindow's attributes seem not to be set correctly
+   * we use thus JSDOMWindow attributes for sizemode and normal window attributes
+   * (and hope for reasonable values when maximized/minimized - since then
+   * outerWidth/outerHeight aren't the dimensions of the restored window)
+   * @param aWindow
+   *        Window reference
+   * @param aAttribute
+   *        String sizemode | width | height | other window attribute
+   * @returns string
+   */
+  _getWindowDimension: function ssi_getWindowDimension(aWindow, aAttribute) {
+    if (aAttribute == "sizemode") {
+      switch (aWindow.windowState) {
+      case aWindow.STATE_FULLSCREEN:
+      case aWindow.STATE_MAXIMIZED:
+        return "maximized";
+      case aWindow.STATE_MINIMIZED:
+        return "minimized";
+      default:
+        return "normal";
+      }
+    }
+
+    var dimension;
+    switch (aAttribute) {
+    case "width":
+      dimension = aWindow.outerWidth;
+      break;
+    case "height":
+      dimension = aWindow.outerHeight;
+      break;
+    default:
+      dimension = aAttribute in aWindow ? aWindow[aAttribute] : "";
+      break;
+    }
+
+    if (aWindow.windowState == aWindow.STATE_NORMAL) {
+      return dimension;
+    }
+    return aWindow.document.documentElement.getAttribute(aAttribute) || dimension;
+  },
+
+  /**
+   * Get nsIURI from string
+   * @param string
+   * @returns nsIURI
+   */
+  _getURIFromString: function ssi_getURIFromString(aString) {
+    return Services.io.newURI(aString, null, null);
+  },
+
+  /**
+   * @param aState is a session state
+   * @param aRecentCrashes is the number of consecutive crashes
+   * @returns whether a restore page will be needed for the session state
+   */
+  _needsRestorePage: function ssi_needsRestorePage(aState, aRecentCrashes) {
+    const SIX_HOURS_IN_MS = 6 * 60 * 60 * 1000;
+
+    // don't display the page when there's nothing to restore
+    let winData = aState.windows || null;
+    if (!winData || winData.length == 0)
+      return false;
+
+    // don't wrap a single about:sessionrestore page
+    if (winData.length == 1 && winData[0].tabs &&
+        winData[0].tabs.length == 1 && winData[0].tabs[0].entries &&
+        winData[0].tabs[0].entries.length == 1 &&
+        winData[0].tabs[0].entries[0].url == "about:sessionrestore")
+      return false;
+
+    // don't automatically restore in Safe Mode
+    if (Services.appinfo.inSafeMode)
+      return true;
+
+    let max_resumed_crashes =
+      this._prefBranch.getIntPref("sessionstore.max_resumed_crashes");
+    let sessionAge = aState.session && aState.session.lastUpdate &&
+                     (Date.now() - aState.session.lastUpdate);
+
+    return max_resumed_crashes != -1 &&
+           (aRecentCrashes > max_resumed_crashes ||
+            sessionAge && sessionAge >= SIX_HOURS_IN_MS);
+  },
+
+  /**
+   * Determine if the tab state we're passed is something we should save. This
+   * is used when closing a tab or closing a window with a single tab
+   *
+   * @param aTabState
+   *        The current tab state
+   * @returns boolean
+   */
+  _shouldSaveTabState: function ssi_shouldSaveTabState(aTabState) {
+    // If the tab has only a transient about: history entry, no other
+    // session history, and no userTypedValue, then we don't actually want to
+    // store this tab's data.
+    return aTabState.entries.length &&
+           !(aTabState.entries.length == 1 &&
+                (aTabState.entries[0].url == "about:blank" ||
+                 aTabState.entries[0].url == "about:newtab") &&
+                 !aTabState.userTypedValue);
+  },
+
+  /**
+   * Determine if we can restore history into this tab.
+   * This will be false when a tab has been removed (usually between
+   * restoreHistoryPrecursor && restoreHistory) or if the tab is still marked
+   * as loading.
+   *
+   * @param aTab
+   * @returns boolean
+   */
+  _canRestoreTabHistory: function ssi_canRestoreTabHistory(aTab) {
+    return aTab.parentNode && aTab.linkedBrowser &&
+           aTab.linkedBrowser.__SS_tabStillLoading;
+  },
+
+  /**
+   * This is going to take a state as provided at startup (via
+   * nsISessionStartup.state) and split it into 2 parts. The first part
+   * (defaultState) will be a state that should still be restored at startup,
+   * while the second part (state) is a state that should be saved for later.
+   * defaultState will be comprised of windows with only pinned tabs, extracted
+   * from state. It will contain the cookies that go along with the history
+   * entries in those tabs. It will also contain window position information.
+   *
+   * defaultState will be restored at startup. state will be placed into
+   * this._lastSessionState and will be kept in case the user explicitly wants
+   * to restore the previous session (publicly exposed as restoreLastSession).
+   *
+   * @param state
+   *        The state, presumably from nsISessionStartup.state
+   * @returns [defaultState, state]
+   */
+  _prepDataForDeferredRestore: function ssi_prepDataForDeferredRestore(state) {
+    // Make sure that we don't modify the global state as provided by
+    // nsSessionStartup.state. Converting the object to a JSON string and
+    // parsing it again is the easiest way to do that, although not the most
+    // efficient one. Deferred sessions that don't have automatic session
+    // restore enabled tend to be a lot smaller though so that this shouldn't
+    // be a big perf hit.
+    state = JSON.parse(JSON.stringify(state));
+
+    let defaultState = { windows: [], selectedWindow: 1 };
+
+    state.selectedWindow = state.selectedWindow || 1;
+
+    // Look at each window, remove pinned tabs, adjust selectedindex,
+    // remove window if necessary.
+    for (let wIndex = 0; wIndex < state.windows.length;) {
+      let window = state.windows[wIndex];
+      window.selected = window.selected || 1;
+      // We're going to put the state of the window into this object
+      let pinnedWindowState = { tabs: [], cookies: []};
+      for (let tIndex = 0; tIndex < window.tabs.length;) {
+        if (window.tabs[tIndex].pinned) {
+          // Adjust window.selected
+          if (tIndex + 1 < window.selected)
+            window.selected -= 1;
+          else if (tIndex + 1 == window.selected)
+            pinnedWindowState.selected = pinnedWindowState.tabs.length + 2;
+            // + 2 because the tab isn't actually in the array yet
+
+          // Now add the pinned tab to our window
+          pinnedWindowState.tabs =
+            pinnedWindowState.tabs.concat(window.tabs.splice(tIndex, 1));
+          // We don't want to increment tIndex here.
+          continue;
+        }
+        tIndex++;
+      }
+
+      // At this point the window in the state object has been modified (or not)
+      // We want to build the rest of this new window object if we have pinnedTabs.
+      if (pinnedWindowState.tabs.length) {
+        // First get the other attributes off the window
+        WINDOW_ATTRIBUTES.forEach(function(attr) {
+          if (attr in window) {
+            pinnedWindowState[attr] = window[attr];
+            delete window[attr];
+          }
+        });
+        // We're just copying position data into the pinned window.
+        // Not copying over:
+        // - _closedTabs
+        // - extData
+        // - isPopup
+        // - hidden
+
+        // Assign a unique ID to correlate the window to be opened with the
+        // remaining data
+        window.__lastSessionWindowID = pinnedWindowState.__lastSessionWindowID
+                                     = "" + Date.now() + Math.random();
+
+        // Extract the cookies that belong with each pinned tab
+        this._splitCookiesFromWindow(window, pinnedWindowState);
+
+        // Actually add this window to our defaultState
+        defaultState.windows.push(pinnedWindowState);
+        // Remove the window from the state if it doesn't have any tabs
+        if (!window.tabs.length) {
+          if (wIndex + 1 <= state.selectedWindow)
+            state.selectedWindow -= 1;
+          else if (wIndex + 1 == state.selectedWindow)
+            defaultState.selectedIndex = defaultState.windows.length + 1;
+
+          state.windows.splice(wIndex, 1);
+          // We don't want to increment wIndex here.
+          continue;
+        }
+
+
+      }
+      wIndex++;
+    }
+
+    return [defaultState, state];
+  },
+
+  /**
+   * Splits out the cookies from aWinState into aTargetWinState based on the
+   * tabs that are in aTargetWinState.
+   * This alters the state of aWinState and aTargetWinState.
+   */
+  _splitCookiesFromWindow:
+    function ssi_splitCookiesFromWindow(aWinState, aTargetWinState) {
+    if (!aWinState.cookies || !aWinState.cookies.length)
+      return;
+
+    // Get the hosts for history entries in aTargetWinState
+    let cookieHosts = {};
+    aTargetWinState.tabs.forEach(function(tab) {
+      tab.entries.forEach(function(entry) {
+        this._extractHostsForCookiesFromEntry(entry, cookieHosts, false);
+      }, this);
+    }, this);
+
+    // By creating a regex we reduce overhead and there is only one loop pass
+    // through either array (cookieHosts and aWinState.cookies).
+    let hosts = Object.keys(cookieHosts).join("|").replace("\\.", "\\.", "g");
+    // If we don't actually have any hosts, then we don't want to do anything.
+    if (!hosts.length)
+      return;
+    let cookieRegex = new RegExp(".*(" + hosts + ")");
+    for (let cIndex = 0; cIndex < aWinState.cookies.length;) {
+      if (cookieRegex.test(aWinState.cookies[cIndex].host)) {
+        aTargetWinState.cookies =
+          aTargetWinState.cookies.concat(aWinState.cookies.splice(cIndex, 1));
+        continue;
+      }
+      cIndex++;
+    }
+  },
+
+  /**
+   * Converts a JavaScript object into a JSON string
+   * (see http://www.json.org/ for more information).
+   *
+   * The inverse operation consists of JSON.parse(JSON_string).
+   *
+   * @param aJSObject is the object to be converted
+   * @returns the object's JSON representation
+   */
+  _toJSONString: function ssi_toJSONString(aJSObject) {
+    return JSON.stringify(aJSObject);
+  },
+
+  _sendRestoreCompletedNotifications: function ssi_sendRestoreCompletedNotifications() {
+    // not all windows restored, yet
+    if (this._restoreCount > 1) {
+      this._restoreCount--;
+      return;
+    }
+
+    // observers were already notified
+    if (this._restoreCount == -1)
+      return;
+
+    // This was the last window restored at startup, notify observers.
+    Services.obs.notifyObservers(null,
+      this._browserSetState ? NOTIFY_BROWSER_STATE_RESTORED : NOTIFY_WINDOWS_RESTORED,
+      "");
+
+    this._browserSetState = false;
+    this._restoreCount = -1;
+  },
+
+   /**
+   * Set the given window's busy state
+   * @param aWindow the window
+   * @param aValue the window's busy state
+   */
+  _setWindowStateBusyValue:
+    function ssi_changeWindowStateBusyValue(aWindow, aValue) {
+
+    this._windows[aWindow.__SSi].busy = aValue;
+
+    // Keep the to-be-restored state in sync because that is returned by
+    // getWindowState() as long as the window isn't loaded, yet.
+    if (!this._isWindowLoaded(aWindow)) {
+      let stateToRestore = this._statesToRestore[aWindow.__SS_restoreID].windows[0];
+      stateToRestore.busy = aValue;
+    }
+  },
+
+  /**
+   * Set the given window's state to 'not busy'.
+   * @param aWindow the window
+   */
+  _setWindowStateReady: function ssi_setWindowStateReady(aWindow) {
+    this._setWindowStateBusyValue(aWindow, false);
+    this._sendWindowStateEvent(aWindow, "Ready");
+  },
+
+  /**
+   * Set the given window's state to 'busy'.
+   * @param aWindow the window
+   */
+  _setWindowStateBusy: function ssi_setWindowStateBusy(aWindow) {
+    this._setWindowStateBusyValue(aWindow, true);
+    this._sendWindowStateEvent(aWindow, "Busy");
+  },
+
+  /**
+   * Dispatch an SSWindowState_____ event for the given window.
+   * @param aWindow the window
+   * @param aType the type of event, SSWindowState will be prepended to this string
+   */
+  _sendWindowStateEvent: function ssi_sendWindowStateEvent(aWindow, aType) {
+    let event = aWindow.document.createEvent("Events");
+    event.initEvent("SSWindowState" + aType, true, false);
+    aWindow.dispatchEvent(event);
+  },
+
+  /**
+   * Dispatch the SSTabRestored event for the given tab.
+   * @param aTab the which has been restored
+   */
+  _sendTabRestoredNotification: function ssi_sendTabRestoredNotification(aTab) {
+      let event = aTab.ownerDocument.createEvent("Events");
+      event.initEvent("SSTabRestored", true, false);
+      aTab.dispatchEvent(event);
+  },
+
+  /**
+   * @param aWindow
+   *        Window reference
+   * @returns whether this window's data is still cached in _statesToRestore
+   *          because it's not fully loaded yet
+   */
+  _isWindowLoaded: function ssi_isWindowLoaded(aWindow) {
+    return !aWindow.__SS_restoreID;
+  },
+
+  /**
+   * Replace "Loading..." with the tab label (with minimal side-effects)
+   * @param aString is the string the title is stored in
+   * @param aTabbrowser is a tabbrowser object, containing aTab
+   * @param aTab is the tab whose title we're updating & using
+   *
+   * @returns aString that has been updated with the new title
+   */
+  _replaceLoadingTitle : function ssi_replaceLoadingTitle(aString, aTabbrowser, aTab) {
+    if (aString == aTabbrowser.mStringBundle.getString("tabs.connecting")) {
+      aTabbrowser.setTabTitle(aTab);
+      [aString, aTab.label] = [aTab.label, aString];
+    }
+    return aString;
+  },
+
+  /**
+   * Resize this._closedWindows to the value of the pref, except in the case
+   * where we don't have any non-popup windows on Windows and Linux. Then we must
+   * resize such that we have at least one non-popup window.
+   */
+  _capClosedWindows : function ssi_capClosedWindows() {
+    if (this._closedWindows.length <= this._max_windows_undo)
+      return;
+    let spliceTo = this._max_windows_undo;
+#ifndef XP_MACOSX
+    let normalWindowIndex = 0;
+    // try to find a non-popup window in this._closedWindows
+    while (normalWindowIndex < this._closedWindows.length &&
+           !!this._closedWindows[normalWindowIndex].isPopup)
+      normalWindowIndex++;
+    if (normalWindowIndex >= this._max_windows_undo)
+      spliceTo = normalWindowIndex + 1;
+#endif
+    this._closedWindows.splice(spliceTo, this._closedWindows.length);
+  },
+
+  _clearRestoringWindows: function ssi_clearRestoringWindows() {
+    for (let i = 0; i < this._closedWindows.length; i++) {
+      delete this._closedWindows[i]._shouldRestore;
+    }
+  },
+
+  /**
+   * Reset state to prepare for a new session state to be restored.
+   */
+  _resetRestoringState: function ssi_initRestoringState() {
+    TabRestoreQueue.reset();
+    this._tabsRestoringCount = 0;
+  },
+
+  /**
+   * Reset the restoring state for a particular tab. This will be called when
+   * removing a tab or when a tab needs to be reset (it's being overwritten).
+   *
+   * @param aTab
+   *        The tab that will be "reset"
+   */
+  _resetTabRestoringState: function ssi_resetTabRestoringState(aTab) {
+    let window = aTab.ownerDocument.defaultView;
+    let browser = aTab.linkedBrowser;
+
+    // Keep the tab's previous state for later in this method
+    let previousState = browser.__SS_restoreState;
+
+    // The browser is no longer in any sort of restoring state.
+    delete browser.__SS_restoreState;
+
+    aTab.removeAttribute("pending");
+    browser.removeAttribute("pending");
+
+    // We want to decrement window.__SS_tabsToRestore here so that we always
+    // decrement it AFTER a tab is done restoring or when a tab gets "reset".
+    window.__SS_tabsToRestore--;
+
+    // Remove the progress listener if we should.
+    this._removeTabsProgressListener(window);
+
+    if (previousState == TAB_STATE_RESTORING) {
+      if (this._tabsRestoringCount)
+        this._tabsRestoringCount--;
+    }
+    else if (previousState == TAB_STATE_NEEDS_RESTORE) {
+      // Make sure the session history listener is removed. This is normally
+      // done in restoreTab, but this tab is being removed before that gets called.
+      this._removeSHistoryListener(aTab);
+
+      // Make sure that the tab is removed from the list of tabs to restore.
+      // Again, this is normally done in restoreTab, but that isn't being called
+      // for this tab.
+      TabRestoreQueue.remove(aTab);
+    }
+  },
+
+  /**
+   * Add the tabs progress listener to the window if it isn't already
+   *
+   * @param aWindow
+   *        The window to add our progress listener to
+   */
+  _ensureTabsProgressListener: function ssi_ensureTabsProgressListener(aWindow) {
+    let tabbrowser = aWindow.gBrowser;
+    if (tabbrowser.mTabsProgressListeners.indexOf(gRestoreTabsProgressListener) == -1)
+      tabbrowser.addTabsProgressListener(gRestoreTabsProgressListener);
+  },
+
+  /**
+   * Attempt to remove the tabs progress listener from the window.
+   *
+   * @param aWindow
+   *        The window from which to remove our progress listener from
+   */
+  _removeTabsProgressListener: function ssi_removeTabsProgressListener(aWindow) {
+    // If there are no tabs left to restore (or restoring) in this window, then
+    // we can safely remove the progress listener from this window.
+    if (!aWindow.__SS_tabsToRestore)
+      aWindow.gBrowser.removeTabsProgressListener(gRestoreTabsProgressListener);
+  },
+
+  /**
+   * Remove the session history listener from the tab's browser if there is one.
+   *
+   * @param aTab
+   *        The tab who's browser to remove the listener
+   */
+  _removeSHistoryListener: function ssi_removeSHistoryListener(aTab) {
+    let browser = aTab.linkedBrowser;
+    if (browser.__SS_shistoryListener) {
+      browser.webNavigation.sessionHistory.
+                            removeSHistoryListener(browser.__SS_shistoryListener);
+      delete browser.__SS_shistoryListener;
+    }
+  }
+};
+
+/**
+ * Priority queue that keeps track of a list of tabs to restore and returns
+ * the tab we should restore next, based on priority rules. We decide between
+ * pinned, visible and hidden tabs in that and FIFO order. Hidden tabs are only
+ * restored with restore_hidden_tabs=true.
+ */
+var TabRestoreQueue = {
+  // The separate buckets used to store tabs.
+  tabs: {priority: [], visible: [], hidden: []},
+
+  // Preferences used by the TabRestoreQueue to determine which tabs
+  // are restored automatically and which tabs will be on-demand.
+  prefs: {
+    // Lazy getter that returns whether tabs are restored on demand.
+    get restoreOnDemand() {
+      let updateValue = () => {
+        let value = Services.prefs.getBoolPref(PREF);
+        let definition = {value: value, configurable: true};
+        Object.defineProperty(this, "restoreOnDemand", definition);
+        return value;
+      }
+
+      const PREF = "browser.sessionstore.restore_on_demand";
+      Services.prefs.addObserver(PREF, updateValue, false);
+      return updateValue();
+    },
+
+    // Lazy getter that returns whether pinned tabs are restored on demand.
+    get restorePinnedTabsOnDemand() {
+      let updateValue = () => {
+        let value = Services.prefs.getBoolPref(PREF);
+        let definition = {value: value, configurable: true};
+        Object.defineProperty(this, "restorePinnedTabsOnDemand", definition);
+        return value;
+      }
+
+      const PREF = "browser.sessionstore.restore_pinned_tabs_on_demand";
+      Services.prefs.addObserver(PREF, updateValue, false);
+      return updateValue();
+    },
+
+    // Lazy getter that returns whether we should restore hidden tabs.
+    get restoreHiddenTabs() {
+      let updateValue = () => {
+        let value = Services.prefs.getBoolPref(PREF);
+        let definition = {value: value, configurable: true};
+        Object.defineProperty(this, "restoreHiddenTabs", definition);
+        return value;
+      }
+
+      const PREF = "browser.sessionstore.restore_hidden_tabs";
+      Services.prefs.addObserver(PREF, updateValue, false);
+      return updateValue();
+    }
+  },
+
+  // Resets the queue and removes all tabs.
+  reset: function () {
+    this.tabs = {priority: [], visible: [], hidden: []};
+  },
+
+  // Adds a tab to the queue and determines its priority bucket.
+  add: function (tab) {
+    let {priority, hidden, visible} = this.tabs;
+
+    if (tab.pinned) {
+      priority.push(tab);
+    } else if (tab.hidden) {
+      hidden.push(tab);
+    } else {
+      visible.push(tab);
+    }
+  },
+
+  // Removes a given tab from the queue, if it's in there.
+  remove: function (tab) {
+    let {priority, hidden, visible} = this.tabs;
+
+    // We'll always check priority first since we don't
+    // have an indicator if a tab will be there or not.
+    let set = priority;
+    let index = set.indexOf(tab);
+
+    if (index == -1) {
+      set = tab.hidden ? hidden : visible;
+      index = set.indexOf(tab);
+    }
+
+    if (index > -1) {
+      set.splice(index, 1);
+    }
+  },
+
+  // Returns and removes the tab with the highest priority.
+  shift: function () {
+    let set;
+    let {priority, hidden, visible} = this.tabs;
+
+    let {restoreOnDemand, restorePinnedTabsOnDemand} = this.prefs;
+    let restorePinned = !(restoreOnDemand && restorePinnedTabsOnDemand);
+    if (restorePinned && priority.length) {
+      set = priority;
+    } else if (!restoreOnDemand) {
+      if (visible.length) {
+        set = visible;
+      } else if (this.prefs.restoreHiddenTabs && hidden.length) {
+        set = hidden;
+      }
+    }
+
+    return set && set.shift();
+  },
+
+  // Moves a given tab from the 'hidden' to the 'visible' bucket.
+  hiddenToVisible: function (tab) {
+    let {hidden, visible} = this.tabs;
+    let index = hidden.indexOf(tab);
+
+    if (index > -1) {
+      hidden.splice(index, 1);
+      visible.push(tab);
+    } else {
+      throw new Error("restore queue: hidden tab not found");
+    }
+  },
+
+  // Moves a given tab from the 'visible' to the 'hidden' bucket.
+  visibleToHidden: function (tab) {
+    let {visible, hidden} = this.tabs;
+    let index = visible.indexOf(tab);
+
+    if (index > -1) {
+      visible.splice(index, 1);
+      hidden.push(tab);
+    } else {
+      throw new Error("restore queue: visible tab not found");
+    }
+  }
+};
+
+// A map storing a closed window's state data until it goes aways (is GC'ed).
+// This ensures that API clients can still read (but not write) states of
+// windows they still hold a reference to but we don't.
+var DyingWindowCache = {
+  _data: new WeakMap(),
+
+  has: function (window) {
+    return this._data.has(window);
+  },
+
+  get: function (window) {
+    return this._data.get(window);
+  },
+
+  set: function (window, data) {
+    this._data.set(window, data);
+  },
+
+  remove: function (window) {
+    this._data.delete(window);
+  }
+};
+
+// A set of tab attributes to persist. We will read a given list of tab
+// attributes when collecting tab data and will re-set those attributes when
+// the given tab data is restored to a new tab.
+var TabAttributes = {
+  _attrs: new Set(),
+
+  // We never want to directly read or write those attributes.
+  // 'image' should not be accessed directly but handled by using the
+  //         gBrowser.getIcon()/setIcon() methods.
+  // 'pending' is used internal by sessionstore and managed accordingly.
+  // 'skipbackgroundnotify' is used internal by tabbrowser.xml.
+  _skipAttrs: new Set(["image", "pending", "skipbackgroundnotify"]),
+
+  persist: function (name) {
+    if (this._attrs.has(name) || this._skipAttrs.has(name)) {
+      return false;
+    }
+
+    this._attrs.add(name);
+    return true;
+  },
+
+  get: function (tab) {
+    let data = {};
+
+    for (let name of this._attrs) {
+      if (tab.hasAttribute(name)) {
+        data[name] = tab.getAttribute(name);
+      }
+    }
+
+    return data;
+  },
+
+  set: function (tab, data = {}) {
+    // Clear attributes.
+    for (let name of this._attrs) {
+      tab.removeAttribute(name);
+    }
+
+    // Set attributes.
+    for (let name in data) {
+      tab.setAttribute(name, data[name]);
+    }
+  }
+};
+
+// This is used to help meter the number of restoring tabs. This is the control
+// point for telling the next tab to restore. It gets attached to each gBrowser
+// via gBrowser.addTabsProgressListener
+var gRestoreTabsProgressListener = {
+  onStateChange: function(aBrowser, aWebProgress, aRequest, aStateFlags, aStatus) {
+    // Ignore state changes on browsers that we've already restored and state
+    // changes that aren't applicable.
+    if (aBrowser.__SS_restoreState &&
+        aBrowser.__SS_restoreState == TAB_STATE_RESTORING &&
+        aStateFlags & Ci.nsIWebProgressListener.STATE_STOP &&
+        aStateFlags & Ci.nsIWebProgressListener.STATE_IS_NETWORK &&
+        aStateFlags & Ci.nsIWebProgressListener.STATE_IS_WINDOW) {
+      // We need to reset the tab before starting the next restore.
+      let win = aBrowser.ownerDocument.defaultView;
+      let tab = win.gBrowser.getTabForBrowser(aBrowser);
+      SessionStoreInternal._resetTabRestoringState(tab);
+      SessionStoreInternal.restoreNextTab();
+    }
+  }
+};
+
+// A SessionStoreSHistoryListener will be attached to each browser before it is
+// restored. We need to catch reloads that occur before the tab is restored
+// because otherwise, docShell will reload an old URI (usually about:blank).
+function SessionStoreSHistoryListener(aTab) {
+  this.tab = aTab;
+}
+SessionStoreSHistoryListener.prototype = {
+  QueryInterface: XPCOMUtils.generateQI([
+    Ci.nsISHistoryListener,
+    Ci.nsISupportsWeakReference
+  ]),
+  browser: null,
+  OnHistoryNewEntry: function(aNewURI) { },
+  OnHistoryGoBack: function(aBackURI) { return true; },
+  OnHistoryGoForward: function(aForwardURI) { return true; },
+  OnHistoryGotoIndex: function(aIndex, aGotoURI) { return true; },
+  OnHistoryPurge: function(aNumEntries) { return true; },
+  OnHistoryReload: function(aReloadURI, aReloadFlags) {
+    // On reload, we want to make sure that session history loads the right
+    // URI. In order to do that, we will juet call restoreTab. That will remove
+    // the history listener and load the right URI.
+    SessionStoreInternal.restoreTab(this.tab);
+    // Returning false will stop the load that docshell is attempting.
+    return false;
+  }
+}
+
+// See toolkit/forgetaboutsite/ForgetAboutSite.jsm
+String.prototype.hasRootDomain = function hasRootDomain(aDomain) {
+  let index = this.indexOf(aDomain);
+  if (index == -1)
+    return false;
+
+  if (this == aDomain)
+    return true;
+
+  let prevChar = this[index - 1];
+  return (index == (this.length - aDomain.length)) &&
+         (prevChar == "." || prevChar == "/");
+}
diff --git a/webbrowser/components/sessionstore/XPathGenerator.jsm b/webbrowser/components/sessionstore/XPathGenerator.jsm
new file mode 100644
index 0000000..83ff2b8
--- /dev/null
+++ b/webbrowser/components/sessionstore/XPathGenerator.jsm
@@ -0,0 +1,97 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+this.EXPORTED_SYMBOLS = ["XPathGenerator"];
+
+this.XPathGenerator = {
+  // these two hashes should be kept in sync
+  namespaceURIs:     { "xhtml": "http://www.w3.org/1999/xhtml" },
+  namespacePrefixes: { "http://www.w3.org/1999/xhtml": "xhtml" },
+
+  /**
+   * Generates an approximate XPath query to an (X)HTML node
+   */
+  generate: function sss_xph_generate(aNode) {
+    // have we reached the document node already?
+    if (!aNode.parentNode)
+      return "";
+
+    // Access localName, namespaceURI just once per node since it's expensive.
+    let nNamespaceURI = aNode.namespaceURI;
+    let nLocalName = aNode.localName;
+
+    let prefix = this.namespacePrefixes[nNamespaceURI] || null;
+    let tag = (prefix ? prefix + ":" : "") + this.escapeName(nLocalName);
+
+    // stop once we've found a tag with an ID
+    if (aNode.id)
+      return "//" + tag + "[@id=" + this.quoteArgument(aNode.id) + "]";
+
+    // count the number of previous sibling nodes of the same tag
+    // (and possible also the same name)
+    let count = 0;
+    let nName = aNode.name || null;
+    for (let n = aNode; (n = n.previousSibling); )
+      if (n.localName == nLocalName && n.namespaceURI == nNamespaceURI &&
+          (!nName || n.name == nName))
+        count++;
+
+    // recurse until hitting either the document node or an ID'd node
+    return this.generate(aNode.parentNode) + "/" + tag +
+           (nName ? "[@name=" + this.quoteArgument(nName) + "]" : "") +
+           (count ? "[" + (count + 1) + "]" : "");
+  },
+
+  /**
+   * Resolves an XPath query generated by XPathGenerator.generate
+   */
+  resolve: function sss_xph_resolve(aDocument, aQuery) {
+    let xptype = Components.interfaces.nsIDOMXPathResult.FIRST_ORDERED_NODE_TYPE;
+    return aDocument.evaluate(aQuery, aDocument, this.resolveNS, xptype, null).singleNodeValue;
+  },
+
+  /**
+   * Namespace resolver for the above XPath resolver
+   */
+  resolveNS: function sss_xph_resolveNS(aPrefix) {
+    return XPathGenerator.namespaceURIs[aPrefix] || null;
+  },
+
+  /**
+   * @returns valid XPath for the given node (usually just the local name itself)
+   */
+  escapeName: function sss_xph_escapeName(aName) {
+    // we can't just use the node's local name, if it contains
+    // special characters (cf. bug 485482)
+    return /^\w+$/.test(aName) ? aName :
+           "*[local-name()=" + this.quoteArgument(aName) + "]";
+  },
+
+  /**
+   * @returns a properly quoted string to insert into an XPath query
+   */
+  quoteArgument: function sss_xph_quoteArgument(aArg) {
+    return !/'/.test(aArg) ? "'" + aArg + "'" :
+           !/"/.test(aArg) ? '"' + aArg + '"' :
+           "concat('" + aArg.replace(/'+/g, "',\"$&\",'") + "')";
+  },
+
+  /**
+   * @returns an XPath query to all savable form field nodes
+   */
+  get restorableFormNodes() {
+    // for a comprehensive list of all available <INPUT> types see
+    // http://mxr.mozilla.org/mozilla-central/search?string=kInputTypeTable
+    let ignoreTypes = ["password", "hidden", "button", "image", "submit", "reset"];
+    // XXXzeniko work-around until lower-case has been implemented (bug 398389)
+    let toLowerCase = '"ABCDEFGHIJKLMNOPQRSTUVWXYZ", "abcdefghijklmnopqrstuvwxyz"';
+    let ignore = "not(translate(@type, " + toLowerCase + ")='" +
+      ignoreTypes.join("' or translate(@type, " + toLowerCase + ")='") + "')";
+    let formNodesXPath = "//textarea|//select|//xhtml:textarea|//xhtml:select|" +
+      "//input[" + ignore + "]|//xhtml:input[" + ignore + "]";
+
+    delete this.restorableFormNodes;
+    return (this.restorableFormNodes = formNodesXPath);
+  }
+};
diff --git a/webbrowser/components/sessionstore/_SessionFile.jsm b/webbrowser/components/sessionstore/_SessionFile.jsm
new file mode 100644
index 0000000..62b4d16
--- /dev/null
+++ b/webbrowser/components/sessionstore/_SessionFile.jsm
@@ -0,0 +1,314 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["_SessionFile"];
+
+/**
+ * Implementation of all the disk I/O required by the session store.
+ * This is a private API, meant to be used only by the session store.
+ * It will change. Do not use it for any other purpose.
+ *
+ * Note that this module implicitly depends on one of two things:
+ * 1. either the asynchronous file I/O system enqueues its requests
+ *   and never attempts to simultaneously execute two I/O requests on
+ *   the files used by this module from two distinct threads; or
+ * 2. the clients of this API are well-behaved and do not place
+ *   concurrent requests to the files used by this module.
+ *
+ * Otherwise, we could encounter bugs, especially under Windows,
+ *   e.g. if a request attempts to write sessionstore.js while
+ *   another attempts to copy that file.
+ *
+ * This implementation uses OS.File, which guarantees property 1.
+ */
+
+const Cu = Components.utils;
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/osfile.jsm");
+Cu.import("resource://gre/modules/Promise.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "NetUtil",
+  "resource://gre/modules/NetUtil.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "FileUtils",
+  "resource://gre/modules/FileUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "Task",
+  "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "console",
+  "resource://gre/modules/Console.jsm");
+
+// An encoder to UTF-8.
+XPCOMUtils.defineLazyGetter(this, "gEncoder", function () {
+  return new TextEncoder();
+});
+// A decoder.
+XPCOMUtils.defineLazyGetter(this, "gDecoder", function () {
+  return new TextDecoder();
+});
+
+this._SessionFile = {
+  /**
+   * A promise fulfilled once initialization (either synchronous or
+   * asynchronous) is complete.
+   */
+  promiseInitialized: function SessionFile_initialized() {
+    return SessionFileInternal.promiseInitialized;
+  },
+  /**
+   * Read the contents of the session file, asynchronously.
+   */
+  read: function SessionFile_read() {
+    return SessionFileInternal.read();
+  },
+  /**
+   * Read the contents of the session file, synchronously.
+   */
+  syncRead: function SessionFile_syncRead() {
+    return SessionFileInternal.syncRead();
+  },
+  /**
+   * Write the contents of the session file, asynchronously.
+   */
+  write: function SessionFile_write(aData) {
+    return SessionFileInternal.write(aData);
+  },
+  /**
+   * Create a backup copy, asynchronously.
+   */
+  createBackupCopy: function SessionFile_createBackupCopy() {
+    return SessionFileInternal.createBackupCopy();
+  },
+  /**
+   * Wipe the contents of the session file, asynchronously.
+   */
+  wipe: function SessionFile_wipe() {
+    return SessionFileInternal.wipe();
+  }
+};
+
+Object.freeze(_SessionFile);
+
+/**
+ * Utilities for dealing with promises and Task.jsm
+ */
+const TaskUtils = {
+  /**
+   * Add logging to a promise.
+   *
+   * @param {Promise} promise
+   * @return {Promise} A promise behaving as |promise|, but with additional
+   * logging in case of uncaught error.
+   */
+  captureErrors: function captureErrors(promise) {
+    return promise.then(
+      null,
+      function onError(reason) {
+        console.error("Uncaught asynchronous error:", reason);
+        throw reason;
+      }
+    );
+  },
+  /**
+   * Spawn a new Task from a generator.
+   *
+   * This function behaves as |Task.spawn|, with the exception that it
+   * adds logging in case of uncaught error. For more information, see
+   * the documentation of |Task.jsm|.
+   *
+   * @param {generator} gen Some generator.
+   * @return {Promise} A promise built from |gen|, with the same semantics
+   * as |Task.spawn(gen)|.
+   */
+  spawn: function spawn(gen) {
+    return this.captureErrors(Task.spawn(gen));
+  }
+};
+
+var SessionFileInternal = {
+  /**
+   * A promise fulfilled once initialization is complete
+   */
+  promiseInitialized: Promise.defer(),
+
+  /**
+   * The path to sessionstore.js
+   */
+  path: OS.Path.join(OS.Constants.Path.profileDir, "sessionstore.js"),
+
+  /**
+   * The path to sessionstore.bak
+   */
+  backupPath: OS.Path.join(OS.Constants.Path.profileDir, "sessionstore.bak"),
+
+  /**
+   * Utility function to safely read a file synchronously.
+   * @param aPath
+   *        A path to read the file from.
+   * @returns string if successful, undefined otherwise.
+   */
+  readAuxSync: function ssfi_readAuxSync(aPath) {
+    let text;
+    try {
+      let file = new FileUtils.File(aPath);
+      let chan = NetUtil.newChannel({
+        uri: NetUtil.newURI(file),
+        loadUsingSystemPrincipal: true
+      });
+      let stream = chan.open();
+      text = NetUtil.readInputStreamToString(stream, stream.available(),
+        {charset: "utf-8"});
+    } catch (e if e.result == Components.results.NS_ERROR_FILE_NOT_FOUND) {
+      // Ignore exceptions about non-existent files.
+    } catch (ex) {
+      // Any other error.
+      console.error("Uncaught error:", ex);
+    } finally {
+      return text;
+    }
+  },
+
+  /**
+   * Read the sessionstore file synchronously.
+   *
+   * This function is meant to serve as a fallback in case of race
+   * between a synchronous usage of the API and asynchronous
+   * initialization.
+   *
+   * In case if sessionstore.js file does not exist or is corrupted (something
+   * happened between backup and write), attempt to read the sessionstore.bak
+   * instead.
+   */
+  syncRead: function ssfi_syncRead() {
+    // First read the sessionstore.js.
+    let text = this.readAuxSync(this.path);
+    if (typeof text === "undefined") {
+      // If sessionstore.js does not exist or is corrupted, read sessionstore.bak.
+      text = this.readAuxSync(this.backupPath);
+    }
+    return text || "";
+  },
+
+  /**
+   * Utility function to safely read a file asynchronously.
+   * @param aPath
+   *        A path to read the file from.
+   * @param aReadOptions
+   *        Read operation options.
+   *        |outExecutionDuration| option will be reused and can be
+   *        incrementally updated by the worker process.
+   * @returns string if successful, undefined otherwise.
+   */
+  readAux: function ssfi_readAux(aPath, aReadOptions) {
+    let self = this;
+    return TaskUtils.spawn(function () {
+      let text;
+      try {
+        let bytes = yield OS.File.read(aPath, undefined, aReadOptions);
+        text = gDecoder.decode(bytes);
+      } catch (ex if self._isNoSuchFile(ex)) {
+        // Ignore exceptions about non-existent files.
+      } catch (ex) {
+        // Any other error.
+        console.error("Uncaught error - with the file: " + self.path, ex);
+      }
+      throw new Task.Result(text);
+    });
+  },
+
+  /**
+   * Read the sessionstore file asynchronously.
+   *
+   * In case sessionstore.js file does not exist or is corrupted (something
+   * happened between backup and write), attempt to read the sessionstore.bak
+   * instead.
+   */
+  read: function ssfi_read() {
+    let self = this;
+    return TaskUtils.spawn(function task() {
+      // Specify |outExecutionDuration| option to hold the combined duration of
+      // the asynchronous reads off the main thread (of both sessionstore.js and
+      // sessionstore.bak, if necessary). If sessionstore.js does not exist or
+      // is corrupted, |outExecutionDuration| will register the time it took to
+      // attempt to read the file. It will then be subsequently incremented by
+      // the read time of sessionsore.bak.
+      let readOptions = {
+        outExecutionDuration: null
+      };
+      // First read the sessionstore.js.
+      let text = yield self.readAux(self.path, readOptions);
+      if (typeof text === "undefined") {
+        // If sessionstore.js does not exist or is corrupted, read the
+        // sessionstore.bak.
+        text = yield self.readAux(self.backupPath, readOptions);
+      }
+      // Return either the content of the sessionstore.bak if it was read
+      // successfully or an empty string otherwise.
+      throw new Task.Result(text || "");
+    });
+  },
+
+  write: function ssfi_write(aData) {
+    let refObj = {};
+    let self = this;
+    return TaskUtils.spawn(function task() {
+      let bytes = gEncoder.encode(aData);
+
+      try {
+        let promise = OS.File.writeAtomic(self.path, bytes, {tmpPath: self.path + ".tmp"});
+        yield promise;
+      } catch (ex) {
+        console.error("Could not write session state file: " + self.path, ex);
+      }
+    });
+  },
+
+  createBackupCopy: function ssfi_createBackupCopy() {
+    let backupCopyOptions = {
+      outExecutionDuration: null
+    };
+    let self = this;
+    return TaskUtils.spawn(function task() {
+      try {
+        yield OS.File.move(self.path, self.backupPath, backupCopyOptions);
+      } catch (ex if self._isNoSuchFile(ex)) {
+        // Ignore exceptions about non-existent files.
+      } catch (ex) {
+        console.error("Could not backup session state file: " + self.path, ex);
+        throw ex;
+      }
+    });
+  },
+
+  wipe: function ssfi_wipe() {
+    let self = this;
+    return TaskUtils.spawn(function task() {
+      try {
+        yield OS.File.remove(self.path);
+      } catch (ex if self._isNoSuchFile(ex)) {
+        // Ignore exceptions about non-existent files.
+      } catch (ex) {
+        console.error("Could not remove session state file: " + self.path, ex);
+        throw ex;
+      }
+
+      try {
+        yield OS.File.remove(self.backupPath);
+      } catch (ex if self._isNoSuchFile(ex)) {
+        // Ignore exceptions about non-existent files.
+      } catch (ex) {
+        console.error("Could not remove session state backup file: " + self.path, ex);
+        throw ex;
+      }
+    });
+  },
+
+  _isNoSuchFile: function ssfi_isNoSuchFile(aReason) {
+    return aReason instanceof OS.File.Error && aReason.becauseNoSuchFile;
+  }
+};
diff --git a/webbrowser/components/sessionstore/content/aboutSessionRestore.js b/webbrowser/components/sessionstore/content/aboutSessionRestore.js
new file mode 100644
index 0000000..2b6f9ea
--- /dev/null
+++ b/webbrowser/components/sessionstore/content/aboutSessionRestore.js
@@ -0,0 +1,320 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+var Cc = Components.classes;
+var Ci = Components.interfaces;
+var Cu = Components.utils;
+
+var gStateObject;
+var gTreeData;
+
+// Page initialization
+
+window.onload = function() {
+  // the crashed session state is kept inside a textbox so that SessionStore picks it up
+  // (for when the tab is closed or the session crashes right again)
+  var sessionData = document.getElementById("sessionData");
+  if (!sessionData.value) {
+    document.getElementById("errorTryAgain").disabled = true;
+    return;
+  }
+
+  // remove unneeded braces (added for compatibility with Firefox 2.0 and 3.0)
+  if (sessionData.value.charAt(0) == '(')
+    sessionData.value = sessionData.value.slice(1, -1);
+  try {
+    gStateObject = JSON.parse(sessionData.value);
+  }
+  catch (exJSON) {
+    var s = new Cu.Sandbox("about:blank", {sandboxName: 'aboutSessionRestore'});
+    gStateObject = Cu.evalInSandbox("(" + sessionData.value + ")", s);
+    // If we couldn't parse the string with JSON.parse originally, make sure
+    // that the value in the textbox will be parsable.
+    sessionData.value = JSON.stringify(gStateObject);
+  }
+
+  // make sure the data is tracked to be restored in case of a subsequent crash
+  var event = document.createEvent("UIEvents");
+  event.initUIEvent("input", true, true, window, 0);
+  sessionData.dispatchEvent(event);
+
+  initTreeView();
+
+  document.getElementById("errorTryAgain").focus();
+};
+
+function initTreeView() {
+  var tabList = document.getElementById("tabList");
+  var winLabel = tabList.getAttribute("_window_label");
+
+  gTreeData = [];
+  gStateObject.windows.forEach(function(aWinData, aIx) {
+    var winState = {
+      label: winLabel.replace("%S", (aIx + 1)),
+      open: true,
+      checked: true,
+      ix: aIx
+    };
+    winState.tabs = aWinData.tabs.map(function(aTabData) {
+      var entry = aTabData.entries[aTabData.index - 1] || { url: "about:blank" };
+      var iconURL = aTabData.attributes && aTabData.attributes.image || null;
+      // don't initiate a connection just to fetch a favicon (see bug 462863)
+      if (/^https?:/.test(iconURL))
+        iconURL = "moz-anno:favicon:" + iconURL;
+      return {
+        label: entry.title || entry.url,
+        checked: true,
+        src: iconURL,
+        parent: winState
+      };
+    });
+    gTreeData.push(winState);
+    for (let tab of winState.tabs)
+      gTreeData.push(tab);
+  }, this);
+
+  tabList.view = treeView;
+  tabList.view.selection.select(0);
+}
+
+// User actions
+
+function restoreSession() {
+  document.getElementById("errorTryAgain").disabled = true;
+
+  // remove all unselected tabs from the state before restoring it
+  var ix = gStateObject.windows.length - 1;
+  for (var t = gTreeData.length - 1; t >= 0; t--) {
+    if (treeView.isContainer(t)) {
+      if (gTreeData[t].checked === 0)
+        // this window will be restored partially
+        gStateObject.windows[ix].tabs =
+          gStateObject.windows[ix].tabs.filter(function(aTabData, aIx)
+                                                 gTreeData[t].tabs[aIx].checked);
+      else if (!gTreeData[t].checked)
+        // this window won't be restored at all
+        gStateObject.windows.splice(ix, 1);
+      ix--;
+    }
+  }
+  var stateString = JSON.stringify(gStateObject);
+
+  var ss = Cc["@mozilla.org/browser/sessionstore;1"].getService(Ci.nsISessionStore);
+  var top = getBrowserWindow();
+
+  // if there's only this page open, reuse the window for restoring the session
+  if (top.gBrowser.tabs.length == 1) {
+    ss.setWindowState(top, stateString, true);
+    return;
+  }
+
+  // restore the session into a new window and close the current tab
+  var newWindow = top.openDialog(top.location, "_blank", "chrome,dialog=no,all");
+  newWindow.addEventListener("load", function() {
+    newWindow.removeEventListener("load", arguments.callee, true);
+    ss.setWindowState(newWindow, stateString, true);
+
+    var tabbrowser = top.gBrowser;
+    var tabIndex = tabbrowser.getBrowserIndexForDocument(document);
+    tabbrowser.removeTab(tabbrowser.tabs[tabIndex]);
+  }, true);
+}
+
+function startNewSession() {
+  var prefBranch = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
+  if (prefBranch.getIntPref("browser.startup.page") == 0)
+    getBrowserWindow().gBrowser.loadURI("about:logopage");
+  else
+    getBrowserWindow().BrowserHome();
+}
+
+function onListClick(aEvent) {
+  // don't react to right-clicks
+  if (aEvent.button == 2)
+    return;
+
+  if (!treeView.treeBox) {
+    return;
+  }
+  var cell = treeView.treeBox.getCellAt(aEvent.clientX, aEvent.clientY);
+  if (cell.col) {
+    // Restore this specific tab in the same window for middle/double/accel clicking
+    // on a tab's title.
+#ifdef XP_MACOSX
+    let accelKey = aEvent.metaKey;
+#else
+    let accelKey = aEvent.ctrlKey;
+#endif
+    if ((aEvent.button == 1 || aEvent.button == 0 && aEvent.detail == 2 || accelKey) &&
+        cell.col.id == "title" &&
+        !treeView.isContainer(cell.row)) {
+      restoreSingleTab(cell.row, aEvent.shiftKey);
+      aEvent.stopPropagation();
+    }
+    else if (cell.col.id == "restore")
+      toggleRowChecked(cell.row);
+  }
+}
+
+function onListKeyDown(aEvent) {
+  switch (aEvent.keyCode)
+  {
+  case KeyEvent.DOM_VK_SPACE:
+    toggleRowChecked(document.getElementById("tabList").currentIndex);
+    break;
+  case KeyEvent.DOM_VK_RETURN:
+    var ix = document.getElementById("tabList").currentIndex;
+    if (aEvent.ctrlKey && !treeView.isContainer(ix))
+      restoreSingleTab(ix, aEvent.shiftKey);
+    break;
+  case KeyEvent.DOM_VK_UP:
+  case KeyEvent.DOM_VK_DOWN:
+  case KeyEvent.DOM_VK_PAGE_UP:
+  case KeyEvent.DOM_VK_PAGE_DOWN:
+  case KeyEvent.DOM_VK_HOME:
+  case KeyEvent.DOM_VK_END:
+    aEvent.preventDefault(); // else the page scrolls unwantedly
+    break;
+  }
+}
+
+// Helper functions
+
+function getBrowserWindow() {
+  return window.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIWebNavigation)
+               .QueryInterface(Ci.nsIDocShellTreeItem).rootTreeItem
+               .QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindow);
+}
+
+function toggleRowChecked(aIx) {
+  var item = gTreeData[aIx];
+  item.checked = !item.checked;
+  treeView.treeBox.invalidateRow(aIx);
+
+  function isChecked(aItem) aItem.checked;
+
+  if (treeView.isContainer(aIx)) {
+    // (un)check all tabs of this window as well
+    for (let tab of item.tabs) {
+      tab.checked = item.checked;
+      treeView.treeBox.invalidateRow(gTreeData.indexOf(tab));
+    }
+  }
+  else {
+    // update the window's checkmark as well (0 means "partially checked")
+    item.parent.checked = item.parent.tabs.every(isChecked) ? true :
+                          item.parent.tabs.some(isChecked) ? 0 : false;
+    treeView.treeBox.invalidateRow(gTreeData.indexOf(item.parent));
+  }
+
+  document.getElementById("errorTryAgain").disabled = !gTreeData.some(isChecked);
+}
+
+function restoreSingleTab(aIx, aShifted) {
+  var tabbrowser = getBrowserWindow().gBrowser;
+  var newTab = tabbrowser.addTab();
+  var item = gTreeData[aIx];
+
+  var ss = Cc["@mozilla.org/browser/sessionstore;1"].getService(Ci.nsISessionStore);
+  var tabState = gStateObject.windows[item.parent.ix]
+                             .tabs[aIx - gTreeData.indexOf(item.parent) - 1];
+  // ensure tab would be visible on the tabstrip.
+  tabState.hidden = false;
+  ss.setTabState(newTab, JSON.stringify(tabState));
+
+  // respect the preference as to whether to select the tab (the Shift key inverses)
+  var prefBranch = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefBranch);
+  if (prefBranch.getBoolPref("browser.tabs.loadInBackground") != !aShifted)
+    tabbrowser.selectedTab = newTab;
+}
+
+// Tree controller
+
+var treeView = {
+  treeBox: null,
+  selection: null,
+
+  get rowCount()                     { return gTreeData.length; },
+  setTree: function(treeBox)         { this.treeBox = treeBox; },
+  getCellText: function(idx, column) { return gTreeData[idx].label; },
+  isContainer: function(idx)         { return "open" in gTreeData[idx]; },
+  getCellValue: function(idx, column){ return gTreeData[idx].checked; },
+  isContainerOpen: function(idx)     { return gTreeData[idx].open; },
+  isContainerEmpty: function(idx)    { return false; },
+  isSeparator: function(idx)         { return false; },
+  isSorted: function()               { return false; },
+  isEditable: function(idx, column)  { return false; },
+  canDrop: function(idx, orientation, dt) { return false; },
+  getLevel: function(idx)            { return this.isContainer(idx) ? 0 : 1; },
+
+  getParentIndex: function(idx) {
+    if (!this.isContainer(idx))
+      for (var t = idx - 1; t >= 0 ; t--)
+        if (this.isContainer(t))
+          return t;
+    return -1;
+  },
+
+  hasNextSibling: function(idx, after) {
+    var thisLevel = this.getLevel(idx);
+    for (var t = after + 1; t < gTreeData.length; t++)
+      if (this.getLevel(t) <= thisLevel)
+        return this.getLevel(t) == thisLevel;
+    return false;
+  },
+
+  toggleOpenState: function(idx) {
+    if (!this.isContainer(idx))
+      return;
+    var item = gTreeData[idx];
+    if (item.open) {
+      // remove this window's tab rows from the view
+      var thisLevel = this.getLevel(idx);
+      for (var t = idx + 1; t < gTreeData.length && this.getLevel(t) > thisLevel; t++);
+      var deletecount = t - idx - 1;
+      gTreeData.splice(idx + 1, deletecount);
+      this.treeBox.rowCountChanged(idx + 1, -deletecount);
+    }
+    else {
+      // add this window's tab rows to the view
+      var toinsert = gTreeData[idx].tabs;
+      for (var i = 0; i < toinsert.length; i++)
+        gTreeData.splice(idx + i + 1, 0, toinsert[i]);
+      this.treeBox.rowCountChanged(idx + 1, toinsert.length);
+    }
+    item.open = !item.open;
+    this.treeBox.invalidateRow(idx);
+  },
+
+  getCellProperties: function(idx, column) {
+    if (column.id == "restore" && this.isContainer(idx) && gTreeData[idx].checked === 0)
+      return "partial";
+    if (column.id == "title")
+      return this.getImageSrc(idx, column) ? "icon" : "noicon";
+
+    return "";
+  },
+
+  getRowProperties: function(idx) {
+    var winState = gTreeData[idx].parent || gTreeData[idx];
+    if (winState.ix % 2 != 0)
+      return "alternate";
+
+    return "";
+  },
+
+  getImageSrc: function(idx, column) {
+    if (column.id == "title")
+      return gTreeData[idx].src || null;
+    return null;
+  },
+
+  getProgressMode : function(idx, column) { },
+  cycleHeader: function(column) { },
+  cycleCell: function(idx, column) { },
+  selectionChanged: function() { },
+  performAction: function(action) { },
+  performActionOnCell: function(action, index, column) { },
+  getColumnProperties: function(column) { return ""; }
+};
diff --git a/webbrowser/components/sessionstore/content/aboutSessionRestore.xhtml b/webbrowser/components/sessionstore/content/aboutSessionRestore.xhtml
new file mode 100644
index 0000000..6b22250
--- /dev/null
+++ b/webbrowser/components/sessionstore/content/aboutSessionRestore.xhtml
@@ -0,0 +1,94 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+-->
+<!DOCTYPE html [
+  <!ENTITY % htmlDTD PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "DTD/xhtml1-strict.dtd">
+  %htmlDTD;
+  <!ENTITY % netErrorDTD SYSTEM "chrome://global/locale/netError.dtd">
+  %netErrorDTD;
+  <!ENTITY % globalDTD SYSTEM "chrome://global/locale/global.dtd">
+  %globalDTD;
+  <!ENTITY % restorepageDTD SYSTEM "chrome://browser/locale/aboutSessionRestore.dtd">
+  %restorepageDTD;
+]>
+
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <head>
+    <title>&restorepage.tabtitle;</title>
+    <link rel="stylesheet" href="chrome://global/skin/netError.css" type="text/css" media="all"/>
+    <link rel="stylesheet" href="chrome://browser/skin/aboutSessionRestore.css" type="text/css" media="all"/>
+    <link rel="icon" type="image/png" href="chrome://global/skin/icons/warning-16.png"/>
+
+    <script type="application/javascript;version=1.8" src="chrome://browser/content/aboutSessionRestore.js"/>
+  </head>
+
+  <body dir="&locale.dir;">
+
+    <!-- PAGE CONTAINER (for styling purposes only) -->
+    <div id="errorPageContainer">
+
+      <!-- Error Title -->
+      <div id="errorTitle">
+        <h1 id="errorTitleText">&restorepage.errorTitle;</h1>
+      </div>
+
+      <!-- LONG CONTENT (the section most likely to require scrolling) -->
+      <div id="errorLongContent">
+
+        <!-- Short Description -->
+        <div id="errorShortDesc">
+          <p id="errorShortDescText">&restorepage.problemDesc;</p>
+        </div>
+
+        <!-- Long Description (Note: See netError.dtd for used XHTML tags) -->
+        <div id="errorLongDesc">
+          <p>&restorepage.tryThis;</p>
+          <ul>
+            <li>&restorepage.restoreSome;</li>
+            <li>&restorepage.startNew;</li>
+          </ul>
+        </div>
+
+        <!-- Short Description -->
+        <div id="errorTrailerDesc">
+          <tree xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+                id="tabList" flex="1" seltype="single" hidecolumnpicker="true"
+                onclick="onListClick(event);" onkeydown="onListKeyDown(event);"
+                _window_label="&restorepage.windowLabel;">
+            <treecols>
+              <treecol cycler="true" id="restore" type="checkbox" label="&restorepage.restoreHeader;"/>
+              <splitter class="tree-splitter"/>
+              <treecol primary="true" id="title" label="&restorepage.listHeader;" flex="1"/>
+            </treecols>
+            <treechildren flex="1"/>
+          </tree>
+        </div>
+      </div>
+
+      <!-- Buttons -->
+      <hbox xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" id="buttons">
+#ifdef XP_UNIX
+        <button id="errorCancel" label="&restorepage.closeButton;"
+                accesskey="&restorepage.close.access;"
+                oncommand="startNewSession();"/>
+        <button id="errorTryAgain" label="&restorepage.tryagainButton;"
+                accesskey="&restorepage.restore.access;"
+                oncommand="restoreSession();"/>
+#else
+        <button id="errorTryAgain" label="&restorepage.tryagainButton;"
+                accesskey="&restorepage.restore.access;"
+                oncommand="restoreSession();"/>
+        <button id="errorCancel" label="&restorepage.closeButton;"
+                accesskey="&restorepage.close.access;"
+                oncommand="startNewSession();"/>
+#endif
+      </hbox>
+      <!-- holds the session data for when the tab is closed -->
+      <input type="text" id="sessionData" style="display: none;"/>
+    </div>
+
+  </body>
+</html>
diff --git a/webbrowser/components/sessionstore/content/content-sessionStore.js b/webbrowser/components/sessionstore/content/content-sessionStore.js
new file mode 100644
index 0000000..e3e956e
--- /dev/null
+++ b/webbrowser/components/sessionstore/content/content-sessionStore.js
@@ -0,0 +1,40 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function debug(msg) {
+  Services.console.logStringMessage("SessionStoreContent: " + msg);
+}
+
+/**
+ * Listens for and handles content events that we need for the
+ * session store service to be notified of state changes in content.
+ */
+var EventListener = {
+
+  DOM_EVENTS: [
+    "pageshow", "change", "input"
+  ],
+
+  init: function () {
+    this.DOM_EVENTS.forEach(e => addEventListener(e, this, true));
+  },
+
+  handleEvent: function (event) {
+    switch (event.type) {
+      case "pageshow":
+        if (event.persisted)
+          sendAsyncMessage("SessionStore:pageshow");
+        break;
+      case "input":
+      case "change":
+        sendAsyncMessage("SessionStore:input");
+        break;
+      default:
+        debug("received unknown event '" + event.type + "'");
+        break;
+    }
+  }
+};
+
+EventListener.init();
diff --git a/webbrowser/components/sessionstore/jar.mn b/webbrowser/components/sessionstore/jar.mn
new file mode 100644
index 0000000..825b00f
--- /dev/null
+++ b/webbrowser/components/sessionstore/jar.mn
@@ -0,0 +1,8 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+browser.jar:
+* content/browser/aboutSessionRestore.xhtml             (content/aboutSessionRestore.xhtml)
+* content/browser/aboutSessionRestore.js                (content/aboutSessionRestore.js)
+  content/browser/content-sessionStore.js               (content/content-sessionStore.js)
diff --git a/webbrowser/components/sessionstore/moz.build b/webbrowser/components/sessionstore/moz.build
new file mode 100644
index 0000000..84278da
--- /dev/null
+++ b/webbrowser/components/sessionstore/moz.build
@@ -0,0 +1,29 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+JAR_MANIFESTS += ['jar.mn']
+
+XPIDL_SOURCES += [
+    'nsISessionStartup.idl',
+    'nsISessionStore.idl',
+]
+
+XPIDL_MODULE = 'sessionstore'
+
+EXTRA_COMPONENTS += [
+    'nsSessionStartup.js',
+    'nsSessionStore.js',
+    'nsSessionStore.manifest',
+]
+
+EXTRA_JS_MODULES.sessionstore = [
+    '_SessionFile.jsm',
+    'DocumentUtils.jsm',
+    'SessionStorage.jsm',
+    'XPathGenerator.jsm',
+]
+
+EXTRA_PP_JS_MODULES.sessionstore += ['SessionStore.jsm']
\ No newline at end of file
diff --git a/webbrowser/components/sessionstore/nsISessionStartup.idl b/webbrowser/components/sessionstore/nsISessionStartup.idl
new file mode 100644
index 0000000..a8e786d
--- /dev/null
+++ b/webbrowser/components/sessionstore/nsISessionStartup.idl
@@ -0,0 +1,59 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/**
+ * nsISessionStore keeps track of the current browsing state - i.e.
+ * tab history, cookies, scroll state, form data, POSTDATA and window features
+ * - and allows to restore everything into one window.
+ */
+
+[scriptable, uuid(51f4b9f0-f3d2-11e2-bb62-2c24dd830245)]
+interface nsISessionStartup: nsISupports
+{
+  /**
+   * Return a promise that is resolved once initialization
+   * is complete.
+   */
+  readonly attribute jsval onceInitialized;
+
+  // Get session state
+  readonly attribute jsval state;
+
+  /**
+   * Determines whether there is a pending session restore and makes sure that
+   * we're initialized before returning. If we're not yet this will read the
+   * session file synchronously.
+   */
+  boolean doRestore();
+
+  /**
+   * Returns whether we will restore a session that ends up replacing the
+   * homepage. The browser uses this to not start loading the homepage if
+   * we're going to stop its load anyway shortly after.
+   *
+   * This is meant to be an optimization for the average case that loading the
+   * session file finishes before we may want to start loading the default
+   * homepage. Should this be called before the session file has been read it
+   * will just return false.
+   */
+  readonly attribute bool willOverrideHomepage;
+
+  /**
+   * What type of session we're restoring.
+   * NO_SESSION       There is no data available from the previous session
+   * RECOVER_SESSION  The last session crashed. It will either be restored or
+   *                  about:sessionrestore will be shown.
+   * RESUME_SESSION   The previous session should be restored at startup
+   * DEFER_SESSION    The previous session is fine, but it shouldn't be restored
+   *                  without explicit action (with the exception of pinned tabs)
+   */
+  const unsigned long NO_SESSION = 0;
+  const unsigned long RECOVER_SESSION = 1;
+  const unsigned long RESUME_SESSION = 2;
+  const unsigned long DEFER_SESSION = 3;
+
+  readonly attribute unsigned long sessionType;
+};
diff --git a/webbrowser/components/sessionstore/nsISessionStore.idl b/webbrowser/components/sessionstore/nsISessionStore.idl
new file mode 100644
index 0000000..0490772
--- /dev/null
+++ b/webbrowser/components/sessionstore/nsISessionStore.idl
@@ -0,0 +1,206 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+interface nsIDOMWindow;
+interface nsIDOMNode;
+
+/**
+ * nsISessionStore keeps track of the current browsing state - i.e.
+ * tab history, cookies, scroll state, form data, POSTDATA and window features
+ * - and allows to restore everything into one browser window.
+ *
+ * The nsISessionStore API operates mostly on browser windows and the tabbrowser
+ * tabs contained in them:
+ *
+ * * "Browser windows" are those DOM windows having loaded
+ * chrome://browser/content/browser.xul . From overlays you can just pass the
+ * global |window| object to the API, though (or |top| from a sidebar).
+ * From elsewhere you can get browser windows through the nsIWindowMediator
+ * by looking for "navigator:browser" windows.
+ *
+ * * "Tabbrowser tabs" are all the child nodes of a browser window's
+ * |gBrowser.tabContainer| such as e.g. |gBrowser.selectedTab|.
+ */
+
+[scriptable, uuid(43ec216b-f002-4424-bfc5-fc555c87dbc4)]
+interface nsISessionStore : nsISupports
+{
+  /**
+   * Initialize the service
+   */
+  jsval init(in nsIDOMWindow aWindow);
+
+  /**
+   * Is it possible to restore the previous session. Will always be false when
+   * in Private Browsing mode.
+   */
+  attribute boolean canRestoreLastSession;
+
+  /**
+   * Restore the previous session if possible. This will not overwrite the
+   * current session. Instead the previous session will be merged into the
+   * current session. Current windows will be reused if they were windows that
+   * pinned tabs were previously restored into. New windows will be opened as
+   * needed.
+   *
+   * Note: This will throw if there is no previous state to restore. Check with
+   * canRestoreLastSession first to avoid thrown errors.
+   */
+  void restoreLastSession();
+
+  /**
+   * Get the current browsing state.
+   * @returns a JSON string representing the session state.
+   */
+  AString getBrowserState();
+
+  /**
+   * Set the browsing state.
+   * This will immediately restore the state of the whole application to the state
+   * passed in, *replacing* the current session.
+   *
+   * @param aState is a JSON string representing the session state.
+   */
+  void setBrowserState(in AString aState);
+
+  /**
+   * @param aWindow is the browser window whose state is to be returned.
+   *
+   * @returns a JSON string representing a session state with only one window.
+   */
+  AString getWindowState(in nsIDOMWindow aWindow);
+
+  /**
+   * @param aWindow    is the browser window whose state is to be set.
+   * @param aState     is a JSON string representing a session state.
+   * @param aOverwrite boolean overwrite existing tabs
+   */
+  void setWindowState(in nsIDOMWindow aWindow, in AString aState, in boolean aOverwrite);
+
+  /**
+   * @param aTab is the tabbrowser tab whose state is to be returned.
+   *
+   * @returns a JSON string representing the state of the tab
+   *         (note: doesn't contain cookies - if you need them, use getWindowState instead).
+   */
+  AString getTabState(in nsIDOMNode aTab);
+
+  /**
+   * @param aTab   is the tabbrowser tab whose state is to be set.
+   * @param aState is a JSON string representing a session state.
+   */
+  void setTabState(in nsIDOMNode aTab, in AString aState);
+
+  /**
+   * Duplicates a given tab as thoroughly as possible.
+   *
+   * @param aWindow is the browser window into which the tab will be duplicated.
+   * @param aTab    is the tabbrowser tab to duplicate (can be from a different window).
+   * @param aDelta  is the offset to the history entry to load in the duplicated tab.
+   * @returns a reference to the newly created tab.
+   */
+  nsIDOMNode duplicateTab(in nsIDOMWindow aWindow, in nsIDOMNode aTab,
+                          [optional] in long aDelta);
+
+  /**
+   * Get the number of restore-able tabs for a browser window
+   */
+  unsigned long getClosedTabCount(in nsIDOMWindow aWindow);
+
+  /**
+   * Get closed tab data
+   *
+   * @param aWindow is the browser window for which to get closed tab data
+   * @returns a JSON string representing the list of closed tabs.
+   */
+  AString getClosedTabData(in nsIDOMWindow aWindow);
+
+  /**
+   * @param aWindow is the browser window to reopen a closed tab in.
+   * @param aIndex  is the index of the tab to be restored (FIFO ordered).
+   * @returns a reference to the reopened tab.
+   */
+  nsIDOMNode undoCloseTab(in nsIDOMWindow aWindow, in unsigned long aIndex);
+
+  /**
+   * @param aWindow is the browser window associated with the closed tab.
+   * @param aIndex  is the index of the closed tab to be removed (FIFO ordered).
+   */
+  nsIDOMNode forgetClosedTab(in nsIDOMWindow aWindow, in unsigned long aIndex);
+
+  /**
+   * Get the number of restore-able windows
+   */
+  unsigned long getClosedWindowCount();
+
+  /**
+   * Get closed windows data
+   *
+   * @returns a JSON string representing the list of closed windows.
+   */
+  AString getClosedWindowData();
+
+  /**
+   * @param aIndex is the index of the windows to be restored (FIFO ordered).
+   * @returns the nsIDOMWindow object of the reopened window
+   */
+  nsIDOMWindow undoCloseWindow(in unsigned long aIndex);
+
+  /**
+   * @param aIndex  is the index of the closed window to be removed (FIFO ordered).
+   *
+   * @throws NS_ERROR_INVALID_ARG
+   *   when aIndex does not map to a closed window
+   */
+  nsIDOMNode forgetClosedWindow(in unsigned long aIndex);
+
+  /**
+   * @param aWindow is the window to get the value for.
+   * @param aKey    is the value's name.
+   *
+   * @returns A string value or an empty string if none is set.
+   */
+  AString getWindowValue(in nsIDOMWindow aWindow, in AString aKey);
+
+  /**
+   * @param aWindow      is the browser window to set the value for.
+   * @param aKey         is the value's name.
+   * @param aStringValue is the value itself (use JSON.stringify/parse before setting JS objects).
+   */
+  void setWindowValue(in nsIDOMWindow aWindow, in AString aKey, in AString aStringValue);
+
+  /**
+   * @param aWindow is the browser window to get the value for.
+   * @param aKey    is the value's name.
+   */
+  void deleteWindowValue(in nsIDOMWindow aWindow, in AString aKey);
+
+  /**
+   * @param aTab is the tabbrowser tab to get the value for.
+   * @param aKey is the value's name.
+   *
+   * @returns A string value or an empty string if none is set.
+   */
+  AString getTabValue(in nsIDOMNode aTab, in AString aKey);
+
+  /**
+   * @param aTab         is the tabbrowser tab to set the value for.
+   * @param aKey         is the value's name.
+   * @param aStringValue is the value itself (use JSON.stringify/parse before setting JS objects).
+   */
+  void setTabValue(in nsIDOMNode aTab, in AString aKey, in AString aStringValue);
+
+  /**
+   * @param aTab is the tabbrowser tab to get the value for.
+   * @param aKey is the value's name.
+   */
+  void deleteTabValue(in nsIDOMNode aTab, in AString aKey);
+
+  /**
+   * @param aName is the name of the attribute to save/restore for all tabbrowser tabs.
+   */
+  void persistTabAttribute(in AString aName);
+};
diff --git a/webbrowser/components/sessionstore/nsSessionStartup.js b/webbrowser/components/sessionstore/nsSessionStartup.js
new file mode 100644
index 0000000..04037c1
--- /dev/null
+++ b/webbrowser/components/sessionstore/nsSessionStartup.js
@@ -0,0 +1,296 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Session Storage and Restoration
+ *
+ * Overview
+ * This service reads user's session file at startup, and makes a determination
+ * as to whether the session should be restored. It will restore the session
+ * under the circumstances described below.  If the auto-start Private Browsing
+ * mode is active, however, the session is never restored.
+ *
+ * Crash Detection
+ * The session file stores a session.state property, that
+ * indicates whether the browser is currently running. When the browser shuts
+ * down, the field is changed to "stopped". At startup, this field is read, and
+ * if its value is "running", then it's assumed that the browser had previously
+ * crashed, or at the very least that something bad happened, and that we should
+ * restore the session.
+ *
+ * Forced Restarts
+ * In the event that a restart is required due to application update or extension
+ * installation, set the browser.sessionstore.resume_session_once pref to true,
+ * and the session will be restored the next time the browser starts.
+ *
+ * Always Resume
+ * This service will always resume the session if the integer pref
+ * browser.startup.page is set to 3.
+ */
+
+/* :::::::: Constants and Helpers ::::::::::::::: */
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cr = Components.results;
+const Cu = Components.utils;
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/PrivateBrowsingUtils.jsm");
+Cu.import("resource://gre/modules/Promise.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "_SessionFile",
+  "resource:///modules/sessionstore/_SessionFile.jsm");
+
+const STATE_RUNNING_STR = "running";
+
+function debug(aMsg) {
+  aMsg = ("SessionStartup: " + aMsg).replace(/\S{80}/g, "$&\n");
+  Services.console.logStringMessage(aMsg);
+}
+
+var gOnceInitializedDeferred = Promise.defer();
+
+/* :::::::: The Service ::::::::::::::: */
+
+function SessionStartup() {
+}
+
+SessionStartup.prototype = {
+
+  // the state to restore at startup
+  _initialState: null,
+  _sessionType: Ci.nsISessionStartup.NO_SESSION,
+  _initialized: false,
+
+/* ........ Global Event Handlers .............. */
+
+  /**
+   * Initialize the component
+   */
+  init: function sss_init() {
+    // do not need to initialize anything in auto-started private browsing sessions
+    if (PrivateBrowsingUtils.permanentPrivateBrowsing) {
+      this._initialized = true;
+      gOnceInitializedDeferred.resolve();
+      return;
+    }
+
+    if (Services.prefs.getBoolPref("browser.sessionstore.resume_session_once") ||
+        Services.prefs.getIntPref("browser.startup.page") == 3) {
+      this._ensureInitialized();
+    } else {
+      _SessionFile.read().then(
+        this._onSessionFileRead.bind(this)
+      );
+    }
+  },
+
+  // Wrap a string as a nsISupports
+  _createSupportsString: function ssfi_createSupportsString(aData) {
+    let string = Cc["@mozilla.org/supports-string;1"]
+                   .createInstance(Ci.nsISupportsString);
+    string.data = aData;
+    return string;
+  },
+
+  _onSessionFileRead: function sss_onSessionFileRead(aStateString) {
+    if (this._initialized) {
+      // Initialization is complete, nothing else to do
+      return;
+    }
+    try {
+      this._initialized = true;
+
+      // Let observers modify the state before it is used
+      let supportsStateString = this._createSupportsString(aStateString);
+      Services.obs.notifyObservers(supportsStateString, "sessionstore-state-read", "");
+      aStateString = supportsStateString.data;
+
+      // No valid session found.
+      if (!aStateString) {
+        this._sessionType = Ci.nsISessionStartup.NO_SESSION;
+        return;
+      }
+
+      // parse the session state into a JS object
+      // remove unneeded braces (added for compatibility with Firefox 2.0 and 3.0)
+      if (aStateString.charAt(0) == '(')
+        aStateString = aStateString.slice(1, -1);
+      let corruptFile = false;
+      try {
+        this._initialState = JSON.parse(aStateString);
+      }
+      catch (ex) {
+        debug("The session file contained un-parse-able JSON: " + ex);
+        // This is not valid JSON, but this might still be valid JavaScript,
+        // as used in FF2/FF3, so we need to eval.
+        // evalInSandbox will throw if aStateString is not parse-able.
+        try {
+          var s = new Cu.Sandbox("about:blank", {sandboxName: 'nsSessionStartup'});
+          this._initialState = Cu.evalInSandbox("(" + aStateString + ")", s);
+        } catch(ex) {
+          debug("The session file contained un-eval-able JSON: " + ex);
+          corruptFile = true;
+        }
+      }
+      let doResumeSessionOnce = Services.prefs.getBoolPref("browser.sessionstore.resume_session_once");
+      let doResumeSession = doResumeSessionOnce ||
+            Services.prefs.getIntPref("browser.startup.page") == 3;
+
+      // If this is a normal restore then throw away any previous session
+      if (!doResumeSessionOnce)
+        delete this._initialState.lastSessionState;
+
+      let resumeFromCrash = Services.prefs.getBoolPref("browser.sessionstore.resume_from_crash");
+      let lastSessionCrashed =
+        this._initialState && this._initialState.session &&
+        this._initialState.session.state &&
+        this._initialState.session.state == STATE_RUNNING_STR;
+
+      // set the startup type
+      if (lastSessionCrashed && resumeFromCrash)
+        this._sessionType = Ci.nsISessionStartup.RECOVER_SESSION;
+      else if (!lastSessionCrashed && doResumeSession)
+        this._sessionType = Ci.nsISessionStartup.RESUME_SESSION;
+      else if (this._initialState)
+        this._sessionType = Ci.nsISessionStartup.DEFER_SESSION;
+      else
+        this._initialState = null; // reset the state
+
+      Services.obs.addObserver(this, "sessionstore-windows-restored", true);
+
+      if (this._sessionType != Ci.nsISessionStartup.NO_SESSION)
+        Services.obs.addObserver(this, "browser:purge-session-history", true);
+
+    } finally {
+      // We're ready. Notify everyone else.
+      Services.obs.notifyObservers(null, "sessionstore-state-finalized", "");
+      gOnceInitializedDeferred.resolve();
+    }
+  },
+
+  /**
+   * Handle notifications
+   */
+  observe: function sss_observe(aSubject, aTopic, aData) {
+    switch (aTopic) {
+    case "app-startup":
+      Services.obs.addObserver(this, "final-ui-startup", true);
+      Services.obs.addObserver(this, "quit-application", true);
+      break;
+    case "final-ui-startup":
+      Services.obs.removeObserver(this, "final-ui-startup");
+      Services.obs.removeObserver(this, "quit-application");
+      this.init();
+      break;
+    case "quit-application":
+      // no reason for initializing at this point (cf. bug 409115)
+      Services.obs.removeObserver(this, "final-ui-startup");
+      Services.obs.removeObserver(this, "quit-application");
+      if (this._sessionType != Ci.nsISessionStartup.NO_SESSION)
+        Services.obs.removeObserver(this, "browser:purge-session-history");
+      break;
+    case "sessionstore-windows-restored":
+      Services.obs.removeObserver(this, "sessionstore-windows-restored");
+      // free _initialState after nsSessionStore is done with it
+      this._initialState = null;
+      break;
+    case "browser:purge-session-history":
+      Services.obs.removeObserver(this, "browser:purge-session-history");
+      // reset all state on sanitization
+      this._sessionType = Ci.nsISessionStartup.NO_SESSION;
+      break;
+    }
+  },
+
+/* ........ Public API ................*/
+
+  get onceInitialized() {
+    return gOnceInitializedDeferred.promise;
+  },
+
+  /**
+   * Get the session state as a jsval
+   */
+  get state() {
+    this._ensureInitialized();
+    return this._initialState;
+  },
+
+  /**
+   * Determines whether there is a pending session restore and makes sure that
+   * we're initialized before returning. If we're not yet this will read the
+   * session file synchronously.
+   * @returns bool
+   */
+  doRestore: function sss_doRestore() {
+    this._ensureInitialized();
+    return this._willRestore();
+  },
+
+  /**
+   * Determines whether there is a pending session restore.
+   * @returns bool
+   */
+  _willRestore: function () {
+    return this._sessionType == Ci.nsISessionStartup.RECOVER_SESSION ||
+           this._sessionType == Ci.nsISessionStartup.RESUME_SESSION;
+  },
+
+  /**
+   * Returns whether we will restore a session that ends up replacing the
+   * homepage. The browser uses this to not start loading the homepage if
+   * we're going to stop its load anyway shortly after.
+   *
+   * This is meant to be an optimization for the average case that loading the
+   * session file finishes before we may want to start loading the default
+   * homepage. Should this be called before the session file has been read it
+   * will just return false.
+   *
+   * @returns bool
+   */
+  get willOverrideHomepage() {
+    if (this._initialState && this._willRestore()) {
+      let windows = this._initialState.windows || null;
+      // If there are valid windows with not only pinned tabs, signal that we
+      // will override the default homepage by restoring a session.
+      return windows && windows.some(w => w.tabs.some(t => !t.pinned));
+    }
+    return false;
+  },
+
+  /**
+   * Get the type of pending session store, if any.
+   */
+  get sessionType() {
+    this._ensureInitialized();
+    return this._sessionType;
+  },
+
+  // Ensure that initialization is complete.
+  // If initialization is not complete yet, fall back to a synchronous
+  // initialization and kill ongoing asynchronous initialization
+  _ensureInitialized: function sss__ensureInitialized() {
+    try {
+      if (this._initialized) {
+        // Initialization is complete, nothing else to do
+        return;
+      }
+      let contents = _SessionFile.syncRead();
+      this._onSessionFileRead(contents);
+    } catch(ex) {
+      debug("ensureInitialized: could not read session " + ex + ", " + ex.stack);
+      throw ex;
+    }
+  },
+
+  /* ........ QueryInterface .............. */
+  QueryInterface : XPCOMUtils.generateQI([Ci.nsIObserver,
+                                          Ci.nsISupportsWeakReference,
+                                          Ci.nsISessionStartup]),
+  classID:          Components.ID("{ec7a6c20-e081-11da-8ad9-0800200c9a66}")
+};
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([SessionStartup]);
diff --git a/webbrowser/components/sessionstore/nsSessionStore.js b/webbrowser/components/sessionstore/nsSessionStore.js
new file mode 100644
index 0000000..38713d5
--- /dev/null
+++ b/webbrowser/components/sessionstore/nsSessionStore.js
@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Session Storage and Restoration
+ *
+ * Overview
+ * This service keeps track of a user's session, storing the various bits
+ * required to return the browser to its current state. The relevant data is
+ * stored in memory, and is periodically saved to disk in a file in the
+ * profile directory. The service is started at first window load, in
+ * delayedStartup, and will restore the session from the data received from
+ * the nsSessionStartup service.
+ */
+
+const Cu = Components.utils;
+const Ci = Components.interfaces;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource:///modules/sessionstore/SessionStore.jsm");
+
+function SessionStoreService() {}
+
+// The SessionStore module's object is frozen. We need to modify our prototype
+// and add some properties so let's just copy the SessionStore object.
+Object.keys(SessionStore).forEach(function (aName) {
+  let desc = Object.getOwnPropertyDescriptor(SessionStore, aName);
+  Object.defineProperty(SessionStoreService.prototype, aName, desc);
+});
+
+SessionStoreService.prototype.classID =
+  Components.ID("{5280606b-2510-4fe0-97ef-9b5a22eafe6b}");
+SessionStoreService.prototype.QueryInterface =
+  XPCOMUtils.generateQI([Ci.nsISessionStore]);
+
+this.NSGetFactory = XPCOMUtils.generateNSGetFactory([SessionStoreService]);
diff --git a/webbrowser/components/sessionstore/nsSessionStore.manifest b/webbrowser/components/sessionstore/nsSessionStore.manifest
new file mode 100644
index 0000000..b136b41
--- /dev/null
+++ b/webbrowser/components/sessionstore/nsSessionStore.manifest
@@ -0,0 +1,18 @@
+# WebappRT doesn't need these instructions, and they don't necessarily work
+# with it, but it does use a GRE directory that the GRE shares with Firefox,
+# so in order to prevent the instructions from being processed for WebappRT,
+# we need to restrict them to the applications that depend on them, i.e.:
+#
+#   b2g:            {3c2e2abc-06d4-11e1-ac3b-374f68613e61}
+#   browser:        {8de7fcbb-c55c-4fbe-bfc5-fc555c87dbc4}
+#   mobile/android: {aa3c5121-dab2-40e2-81ca-7ea25febc110}
+#   mobile/xul:     {a23983c0-fd0e-11dc-95ff-0800200c9a66}
+#
+# In theory we should do this for all these instructions, but in practice it is
+# sufficient to do it for the app-startup one, and the file is simpler that way.
+
+component {5280606b-2510-4fe0-97ef-9b5a22eafe6b} nsSessionStore.js
+contract @mozilla.org/browser/sessionstore;1 {5280606b-2510-4fe0-97ef-9b5a22eafe6b}
+component {ec7a6c20-e081-11da-8ad9-0800200c9a66} nsSessionStartup.js
+contract @mozilla.org/browser/sessionstartup;1 {ec7a6c20-e081-11da-8ad9-0800200c9a66}
+category app-startup nsSessionStartup service,@mozilla.org/browser/sessionstartup;1 application={3c2e2abc-06d4-11e1-ac3b-374f68613e61} application={8de7fcbb-c55c-4fbe-bfc5-fc555c87dbc4} application={aa3c5121-dab2-40e2-81ca-7ea25febc110} application={a23983c0-fd0e-11dc-95ff-0800200c9a66}