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diff --git a/toolkit/components/url-classifier/content/moz/alarm.js b/toolkit/components/url-classifier/content/moz/alarm.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/.
+
+
+// An Alarm fires a callback after a certain amount of time, or at
+// regular intervals. It's a convenient replacement for
+// setTimeout/Interval when you don't want to bind to a specific
+// window.
+//
+// The ConditionalAlarm is an Alarm that cancels itself if its callback 
+// returns a value that type-converts to true.
+//
+// Example:
+//
+//  function foo() { dump('hi'); };
+//  new G_Alarm(foo, 10*1000);                   // Fire foo in 10 seconds
+//  new G_Alarm(foo, 10*1000, true /*repeat*/);  // Fire foo every 10 seconds
+//  new G_Alarm(foo, 10*1000, true, 7);          // Fire foo every 10 seconds
+//                                               // seven times
+//  new G_ConditionalAlarm(foo, 1000, true); // Fire every sec until foo()==true
+//
+//  // Fire foo every 10 seconds until foo returns true or until it fires seven
+//  // times, whichever happens first.
+//  new G_ConditionalAlarm(foo, 10*1000, true /*repeating*/, 7);
+//
+// TODO: maybe pass an isFinal flag to the callback if they opted to
+// set maxTimes and this is the last iteration?
+
+
+/**
+ * Set an alarm to fire after a given amount of time, or at specific 
+ * intervals.
+ *
+ * @param callback Function to call when the alarm fires
+ * @param delayMS Number indicating the length of the alarm period in ms
+ * @param opt_repeating Boolean indicating whether this should fire 
+ *                      periodically
+ * @param opt_maxTimes Number indicating a maximum number of times to 
+ *                     repeat (obviously only useful when opt_repeating==true)
+ */
+this.G_Alarm =
+function G_Alarm(callback, delayMS, opt_repeating, opt_maxTimes) {
+  this.debugZone = "alarm";
+  this.callback_ = callback;
+  this.repeating_ = !!opt_repeating;
+  this.timer_ = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+  var type = opt_repeating ? 
+             this.timer_.TYPE_REPEATING_SLACK : 
+             this.timer_.TYPE_ONE_SHOT;
+  this.maxTimes_ = opt_maxTimes ? opt_maxTimes : null;
+  this.nTimes_ = 0;
+
+  this.observerServiceObserver_ = new G_ObserverServiceObserver(
+                                        'xpcom-shutdown',
+                                        BindToObject(this.cancel, this));
+
+  // Ask the timer to use nsITimerCallback (.notify()) when ready
+  this.timer_.initWithCallback(this, delayMS, type);
+}
+
+/**
+ * Cancel this timer 
+ */
+G_Alarm.prototype.cancel = function() {
+  if (!this.timer_) {
+    return;
+  }
+
+  this.timer_.cancel();
+  // Break circular reference created between this.timer_ and the G_Alarm
+  // instance (this)
+  this.timer_ = null;
+  this.callback_ = null;
+
+  // We don't need the shutdown observer anymore
+  this.observerServiceObserver_.unregister();
+}
+
+/**
+ * Invoked by the timer when it fires
+ * 
+ * @param timer Reference to the nsITimer which fired (not currently 
+ *              passed along)
+ */
+G_Alarm.prototype.notify = function(timer) {
+  // fire callback and save results
+  var ret = this.callback_();
+  
+  // If they've given us a max number of times to fire, enforce it
+  this.nTimes_++;
+  if (this.repeating_ && 
+      typeof this.maxTimes_ == "number" 
+      && this.nTimes_ >= this.maxTimes_) {
+    this.cancel();
+  } else if (!this.repeating_) {
+    // Clear out the callback closure for TYPE_ONE_SHOT timers
+    this.cancel();
+  }
+  // We don't cancel/cleanup timers that repeat forever until either
+  // xpcom-shutdown occurs or cancel() is called explicitly.
+
+  return ret;
+}
+
+G_Alarm.prototype.setDelay = function(delay) {
+  this.timer_.delay = delay;
+}
+
+/**
+ * XPCOM cruft
+ */
+G_Alarm.prototype.QueryInterface = function(iid) {
+  if (iid.equals(Components.interfaces.nsISupports) ||
+      iid.equals(Components.interfaces.nsITimerCallback))
+    return this;
+
+  throw Components.results.NS_ERROR_NO_INTERFACE;
+}
+
+
+/**
+ * An alarm with the additional property that it cancels itself if its 
+ * callback returns true.
+ *
+ * For parameter documentation, see G_Alarm
+ */
+this.G_ConditionalAlarm =
+function G_ConditionalAlarm(callback, delayMS, opt_repeating, opt_maxTimes) {
+  G_Alarm.call(this, callback, delayMS, opt_repeating, opt_maxTimes);
+  this.debugZone = "conditionalalarm";
+}
+
+G_ConditionalAlarm.inherits = function(parentCtor) {
+  var tempCtor = function(){};
+  tempCtor.prototype = parentCtor.prototype;
+  this.superClass_ = parentCtor.prototype;
+  this.prototype = new tempCtor();
+}
+
+G_ConditionalAlarm.inherits(G_Alarm);
+
+/**
+ * Invoked by the timer when it fires
+ * 
+ * @param timer Reference to the nsITimer which fired (not currently 
+ *              passed along)
+ */
+G_ConditionalAlarm.prototype.notify = function(timer) {
+  // Call G_Alarm::notify
+  var rv = G_Alarm.prototype.notify.call(this, timer);
+
+  if (this.repeating_ && rv) {
+    G_Debug(this, "Callback of a repeating alarm returned true; cancelling.");
+    this.cancel();
+  }
+}