Add base::RunLoop and update ui_test_utils to use it to reduce flakiness

ui/ui_controls/ui_controls_internal_win.cc

 // Copyright (c) 2012 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 "ui/ui_controls/ui_controls_internal_win.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
@@ skipping 94 matching lines @@
 void UninstallHook(InputDispatcher* dispatcher) {
   if (current_dispatcher_ == dispatcher) {
     installed_hook_ = false;
     current_dispatcher_ = NULL;
     UnhookWindowsHookEx(next_hook_);
   }
 }
 
 InputDispatcher::InputDispatcher(const base::Closure& task,
                                  UINT message_waiting_for)
     : task_(task), message_waiting_for_(message_waiting_for) {

[jar (doing other things), 2012/06/08 01:05:37]

nit: one init per line

   InstallHook(this, message_waiting_for == WM_KEYUP);
 }
 
 InputDispatcher::~InputDispatcher() {
   // Make sure the hook isn't installed.
   UninstallHook(this);
 }
 
 void InputDispatcher::DispatchedMessage(WPARAM message) {
   if (message == message_waiting_for_)
     MatchingMessageFound();
 }
 
 void InputDispatcher::MatchingMessageFound() {
   UninstallHook(this);
   // At the time we're invoked the event has not actually been processed.
   // Use PostTask to make sure the event has been processed before notifying.
   MessageLoop::current()->PostTask(
       FROM_HERE, base::Bind(&InputDispatcher::NotifyTask, this));
 }
 
 void InputDispatcher::NotifyTask() {
-  task_.Run();
+  if (!task_.is_null()) {
+    task_.Run();
+    task_.Reset();

[jar (doing other things), 2012/06/08 01:05:37]

Why did this change?

[jbates, 2012/06/13 22:11:20]

I'll undo this.  I just noticed there's a DCHECK in Release if it's called too
many times so no need for this code.

+  }
   Release();
 }
 
 // Private functions ----------------------------------------------------------
 
 // Populate the INPUT structure with the appropriate keyboard event
 // parameters required by SendInput
 bool FillKeyboardInput(ui::KeyboardCode key, INPUT* input, bool key_up) {
   memset(input, 0, sizeof(INPUT));
   input->type = INPUT_KEYBOARD;
@@ skipping 189 matching lines @@
     return false;
 
   if (dispatcher.get())
     dispatcher->AddRef();
 
   return true;
 }
 
 }  // namespace internal
 }  // namespace ui_controls