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diff --git a/toolkit/components/url-classifier/content/moz/observer.js b/toolkit/components/url-classifier/content/moz/observer.js
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+# 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/.
+
+
+// A couple of classes to simplify creating observers. 
+//
+// Example1:
+//
+// function doSomething() { ... }
+// var observer = new G_ObserverWrapper(topic, doSomething);
+// someObj.addObserver(topic, observer);
+//
+// Example2: 
+//
+// function doSomething() { ... }
+// new G_ObserverServiceObserver("profile-after-change", 
+//                               doSomething,
+//                               true /* run only once */);
+
+
+/**
+ * This class abstracts the admittedly simple boilerplate required of
+ * an nsIObserver. It saves you the trouble of implementing the
+ * indirection of your own observe() function.
+ *
+ * @param topic String containing the topic the observer will filter for
+ *
+ * @param observeFunction Reference to the function to call when the 
+ *                        observer fires
+ *
+ * @constructor
+ */
+this.G_ObserverWrapper = function G_ObserverWrapper(topic, observeFunction) {
+  this.debugZone = "observer";
+  this.topic_ = topic;
+  this.observeFunction_ = observeFunction;
+}
+
+/**
+ * XPCOM
+ */
+G_ObserverWrapper.prototype.QueryInterface = function(iid) {
+  if (iid.equals(Ci.nsISupports) || iid.equals(Ci.nsIObserver))
+    return this;
+  throw Components.results.NS_ERROR_NO_INTERFACE;
+}
+
+/**
+ * Invoked by the thingy being observed
+ */
+G_ObserverWrapper.prototype.observe = function(subject, topic, data) {
+  if (topic == this.topic_)
+    this.observeFunction_(subject, topic, data);
+}
+
+
+/**
+ * This class abstracts the admittedly simple boilerplate required of
+ * observing an observerservice topic. It implements the indirection
+ * required, and automatically registers to hear the topic.
+ *
+ * @param topic String containing the topic the observer will filter for
+ *
+ * @param observeFunction Reference to the function to call when the 
+ *                        observer fires
+ *
+ * @param opt_onlyOnce Boolean indicating if the observer should unregister
+ *                     after it has fired
+ *
+ * @constructor
+ */
+this.G_ObserverServiceObserver =
+function G_ObserverServiceObserver(topic, observeFunction, opt_onlyOnce) {
+  this.debugZone = "observerserviceobserver";
+  this.topic_ = topic;
+  this.observeFunction_ = observeFunction;
+  this.onlyOnce_ = !!opt_onlyOnce;
+  
+  this.observer_ = new G_ObserverWrapper(this.topic_, 
+                                         BindToObject(this.observe_, this));
+  this.observerService_ = Cc["@mozilla.org/observer-service;1"]
+                          .getService(Ci.nsIObserverService);
+  this.observerService_.addObserver(this.observer_, this.topic_, false);
+}
+
+/**
+ * Unregister the observer from the observerservice
+ */
+G_ObserverServiceObserver.prototype.unregister = function() {
+  this.observerService_.removeObserver(this.observer_, this.topic_);
+  this.observerService_ = null;
+}
+
+/**
+ * Invoked by the observerservice
+ */
+G_ObserverServiceObserver.prototype.observe_ = function(subject, topic, data) {
+  this.observeFunction_(subject, topic, data);
+  if (this.onlyOnce_)
+    this.unregister();
+}
+
+#ifdef DEBUG
+this.TEST_G_Observer = function TEST_G_Observer() {
+  if (G_GDEBUG) {
+
+    var z = "observer UNITTEST";
+    G_debugService.enableZone(z);
+
+    G_Debug(z, "Starting");
+
+    var regularObserverRan = 0;
+    var observerServiceObserverRan = 0;
+
+    let regularObserver = function () {
+      regularObserverRan++;
+    };
+
+    let observerServiceObserver = function () {
+      observerServiceObserverRan++;
+    };
+
+    var service = Cc["@mozilla.org/observer-service;1"]
+                  .getService(Ci.nsIObserverService);
+    var topic = "google-observer-test";
+
+    var o1 = new G_ObserverWrapper(topic, regularObserver);
+    service.addObserver(o1, topic, false);
+
+    new G_ObserverServiceObserver(topic, 
+                                  observerServiceObserver, true /* once */);
+
+    // Notifications happen synchronously, so this is easy
+    service.notifyObservers(null, topic, null);
+    service.notifyObservers(null, topic, null);
+
+    G_Assert(z, regularObserverRan == 2, "Regular observer broken");
+    G_Assert(z, observerServiceObserverRan == 1, "ObsServObs broken");
+
+    service.removeObserver(o1, topic);
+    G_Debug(z, "PASSED");
+  }
+}
+#endif