1 files changed, 71 insertions, 0 deletions
diff --git a/devtools/shared/content-observer.js b/devtools/shared/content-observer.js
new file mode 100644
index 000000000..6bef2ebd5
--- /dev/null
+++ b/devtools/shared/content-observer.js
@@ -0,0 +1,71 @@
+/* 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";
+
+const {Cc, Ci, Cu, Cr} = require("chrome");
+const Services = require("Services");
+
+const events = require("sdk/event/core");
+
+/**
+ * Handles adding an observer for the creation of content document globals,
+ * event sent immediately after a web content document window has been set up,
+ * but before any script code has been executed.
+ */
+function ContentObserver(tabActor) {
+  this._contentWindow = tabActor.window;
+  this._onContentGlobalCreated = this._onContentGlobalCreated.bind(this);
+  this._onInnerWindowDestroyed = this._onInnerWindowDestroyed.bind(this);
+  this.startListening();
+}
+
+module.exports.ContentObserver = ContentObserver;
+
+ContentObserver.prototype = {
+  /**
+   * Starts listening for the required observer messages.
+   */
+  startListening: function () {
+    Services.obs.addObserver(
+      this._onContentGlobalCreated, "content-document-global-created", false);
+    Services.obs.addObserver(
+      this._onInnerWindowDestroyed, "inner-window-destroyed", false);
+  },
+
+  /**
+   * Stops listening for the required observer messages.
+   */
+  stopListening: function () {
+    Services.obs.removeObserver(
+      this._onContentGlobalCreated, "content-document-global-created", false);
+    Services.obs.removeObserver(
+      this._onInnerWindowDestroyed, "inner-window-destroyed", false);
+  },
+
+  /**
+   * Fired immediately after a web content document window has been set up.
+   */
+  _onContentGlobalCreated: function (subject, topic, data) {
+    if (subject == this._contentWindow) {
+      events.emit(this, "global-created", subject);
+    }
+  },
+
+  /**
+   * Fired when an inner window is removed from the backward/forward cache.
+   */
+  _onInnerWindowDestroyed: function (subject, topic, data) {
+    let id = subject.QueryInterface(Ci.nsISupportsPRUint64).data;
+    events.emit(this, "global-destroyed", id);
+  }
+};
+
+// Utility functions.
+
+ContentObserver.GetInnerWindowID = function (window) {
+  return window
+    .QueryInterface(Ci.nsIInterfaceRequestor)
+    .getInterface(Ci.nsIDOMWindowUtils)
+    .currentInnerWindowID;
+};