Fix a bug where content scripts would get run twice in some cases.

chrome/renderer/user_script_idle_scheduler.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/user_script_idle_scheduler.h"
 
 #include "base/message_loop.h"
 #include "chrome/renderer/render_view.h"
 
 namespace {
@@ skipping 19 matching lines @@
   MessageLoop::current()->PostTask(FROM_HERE,
       method_factory_.NewRunnableMethod(&UserScriptIdleScheduler::MaybeRun));
 }
 
 void UserScriptIdleScheduler::Cancel() {
   view_ = NULL;
   frame_ = NULL;
 }
 
 void UserScriptIdleScheduler::MaybeRun() {
-  if (!view_)
+  if (!view_ || has_run())
     return;
 
+  // Note: we must set this before calling OnUserScriptIdleTriggered, because
+  // that may result in a synchronous call back into MaybeRun if there is a
+  // pending task currently in the queue.
+  // http://code.google.com/p/chromium/issues/detail?id=29644
+  has_run_ = true;
+
   DCHECK(frame_);
   view_->OnUserScriptIdleTriggered(frame_);
   Cancel();
-  has_run_ = true;
 }