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diff --git a/browser/components/newtab/NewTabWebChannel.jsm b/browser/components/newtab/NewTabWebChannel.jsm
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+++ b/browser/components/newtab/NewTabWebChannel.jsm
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+/* global
+ NewTabPrefsProvider,
+ Services,
+ EventEmitter,
+ Preferences,
+ XPCOMUtils,
+ WebChannel,
+ NewTabRemoteResources
+*/
+/* exported NewTabWebChannel */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["NewTabWebChannel"];
+
+const {utils: Cu} = Components;
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/Preferences.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "NewTabPrefsProvider",
+ "resource:///modules/NewTabPrefsProvider.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "NewTabRemoteResources",
+ "resource:///modules/NewTabRemoteResources.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "WebChannel",
+ "resource://gre/modules/WebChannel.jsm");
+XPCOMUtils.defineLazyGetter(this, "EventEmitter", function() {
+ const {EventEmitter} = Cu.import("resource://devtools/shared/event-emitter.js", {});
+ return EventEmitter;
+});
+
+const CHAN_ID = "newtab";
+const PREF_ENABLED = "browser.newtabpage.remote";
+const PREF_MODE = "browser.newtabpage.remote.mode";
+
+/**
+ * NewTabWebChannel is the conduit for all communication with unprivileged newtab instances.
+ *
+ * It allows for the ability to broadcast to all newtab browsers.
+ * If the browser.newtab.remote pref is false, the object will be in an uninitialized state.
+ *
+ * Mode choices:
+ * 'production': pages from our production CDN
+ * 'staging': pages from our staging CDN
+ * 'test': intended for tests
+ * 'test2': intended for tests
+ * 'dev': intended for development
+ *
+ * An unknown mode will result in 'production' mode, which is the default
+ *
+ * Incoming messages are expected to be JSON-serialized and in the format:
+ *
+ * {
+ * type: "REQUEST_SCREENSHOT",
+ * data: {
+ * url: "https://example.com"
+ * }
+ * }
+ *
+ * Or:
+ *
+ * {
+ * type: "REQUEST_SCREENSHOT",
+ * }
+ *
+ * Outgoing messages are expected to be objects serializable by structured cloning, in a similar format:
+ * {
+ * type: "RECEIVE_SCREENSHOT",
+ * data: {
+ * "url": "https://example.com",
+ * "image": "dataURi:....."
+ * }
+ * }
+ */
+let NewTabWebChannelImpl = function NewTabWebChannelImpl() {
+ EventEmitter.decorate(this);
+ this._handlePrefChange = this._handlePrefChange.bind(this);
+ this._incomingMessage = this._incomingMessage.bind(this);
+};
+
+NewTabWebChannelImpl.prototype = {
+ _prefs: {},
+ _channel: null,
+
+ // a WeakMap containing browsers as keys and a weak ref to their principal
+ // as value
+ _principals: null,
+
+ // a Set containing weak refs to browsers
+ _browsers: null,
+
+ /*
+ * Returns current channel's ID
+ */
+ get chanId() {
+ return CHAN_ID;
+ },
+
+ /*
+ * Returns the number of browsers currently tracking
+ */
+ get numBrowsers() {
+ return this._getBrowserRefs().length;
+ },
+
+ /*
+ * Returns current channel's origin
+ */
+ get origin() {
+ if (!(this._prefs.mode in NewTabRemoteResources.MODE_CHANNEL_MAP)) {
+ this._prefs.mode = "production";
+ }
+ return NewTabRemoteResources.MODE_CHANNEL_MAP[this._prefs.mode].origin;
+ },
+
+ /*
+ * Unloads all browsers and principals
+ */
+ _unloadAll() {
+ if (this._principals != null) {
+ this._principals = new WeakMap();
+ }
+ this._browsers = new Set();
+ this.emit("targetUnloadAll");
+ },
+
+ /*
+ * Checks if a browser is known
+ *
+ * This will cause an iteration through all known browsers.
+ * That's ok, we don't expect a lot of browsers
+ */
+ _isBrowserKnown(browser) {
+ for (let bRef of this._getBrowserRefs()) {
+ let b = bRef.get();
+ if (b && b.permanentKey === browser.permanentKey) {
+ return true;
+ }
+ }
+
+ return false;
+ },
+
+ /*
+ * Obtains all known browser refs
+ */
+ _getBrowserRefs() {
+ // Some code may try to emit messages after teardown.
+ if (!this._browsers) {
+ return [];
+ }
+ let refs = [];
+ for (let bRef of this._browsers) {
+ /*
+ * even though we hold a weak ref to browser, it seems that browser
+ * objects aren't gc'd immediately after a tab closes. They stick around
+ * in memory, but thankfully they don't have a documentURI in that case
+ */
+ let browser = bRef.get();
+ if (browser && browser.documentURI) {
+ refs.push(bRef);
+ } else {
+ // need to clean up principals because the browser object is not gc'ed
+ // immediately
+ this._principals.delete(browser);
+ this._browsers.delete(bRef);
+ this.emit("targetUnload");
+ }
+ }
+ return refs;
+ },
+
+ /*
+ * Receives a message from content.
+ *
+ * Keeps track of browsers for broadcast, relays messages to listeners.
+ */
+ _incomingMessage(id, message, target) {
+ if (this.chanId !== id) {
+ Cu.reportError(new Error("NewTabWebChannel unexpected message destination"));
+ }
+
+ /*
+ * need to differentiate by browser, because event targets are created each
+ * time a message is sent.
+ */
+ if (!this._isBrowserKnown(target.browser)) {
+ this._browsers.add(Cu.getWeakReference(target.browser));
+ this._principals.set(target.browser, Cu.getWeakReference(target.principal));
+ this.emit("targetAdd");
+ }
+
+ try {
+ let msg = JSON.parse(message);
+ this.emit(msg.type, {data: msg.data, target: target});
+ } catch (err) {
+ Cu.reportError(err);
+ }
+ },
+
+ /*
+ * Sends a message to all known browsers
+ */
+ broadcast(actionType, message) {
+ for (let bRef of this._getBrowserRefs()) {
+ let browser = bRef.get();
+ try {
+ let principal = this._principals.get(browser).get();
+ if (principal && browser && browser.documentURI) {
+ this._channel.send({type: actionType, data: message}, {browser, principal});
+ }
+ } catch (e) {
+ Cu.reportError(new Error("NewTabWebChannel WeakRef is dead"));
+ this._principals.delete(browser);
+ }
+ }
+ },
+
+ /*
+ * Sends a message to a specific target
+ */
+ send(actionType, message, target) {
+ try {
+ this._channel.send({type: actionType, data: message}, target);
+ } catch (e) {
+ // Web Channel might be dead
+ Cu.reportError(e);
+ }
+ },
+
+ /*
+ * Pref change observer callback
+ */
+ _handlePrefChange(prefName, newState, forceState) { // eslint-disable-line no-unused-vars
+ switch (prefName) {
+ case PREF_ENABLED:
+ if (!this._prefs.enabled && newState) {
+ // changing state from disabled to enabled
+ this.setupState();
+ } else if (this._prefs.enabled && !newState) {
+ // changing state from enabled to disabled
+ this.tearDownState();
+ }
+ break;
+ case PREF_MODE:
+ if (this._prefs.mode !== newState) {
+ // changing modes
+ this.tearDownState();
+ this.setupState();
+ }
+ break;
+ }
+ },
+
+ /*
+ * Sets up the internal state
+ */
+ setupState() {
+ this._prefs.enabled = Preferences.get(PREF_ENABLED, false);
+
+ let mode = Preferences.get(PREF_MODE, "production");
+ if (!(mode in NewTabRemoteResources.MODE_CHANNEL_MAP)) {
+ mode = "production";
+ }
+ this._prefs.mode = mode;
+ this._principals = new WeakMap();
+ this._browsers = new Set();
+
+ if (this._prefs.enabled) {
+ this._channel = new WebChannel(this.chanId, Services.io.newURI(this.origin, null, null));
+ this._channel.listen(this._incomingMessage);
+ }
+ },
+
+ tearDownState() {
+ if (this._channel) {
+ this._channel.stopListening();
+ }
+ this._prefs = {};
+ this._unloadAll();
+ this._channel = null;
+ this._principals = null;
+ this._browsers = null;
+ },
+
+ init() {
+ this.setupState();
+ NewTabPrefsProvider.prefs.on(PREF_ENABLED, this._handlePrefChange);
+ NewTabPrefsProvider.prefs.on(PREF_MODE, this._handlePrefChange);
+ },
+
+ uninit() {
+ this.tearDownState();
+ NewTabPrefsProvider.prefs.off(PREF_ENABLED, this._handlePrefChange);
+ NewTabPrefsProvider.prefs.off(PREF_MODE, this._handlePrefChange);
+ }
+};
+
+let NewTabWebChannel = new NewTabWebChannelImpl();