Disallow UI/IO thread blocking on any other thread.

chrome/browser/automation/testing_automation_provider.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 "chrome/browser/automation/testing_automation_provider.h"
 
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 305 matching lines @@
     const content::NotificationDetails& details) {
   DCHECK(type == chrome::NOTIFICATION_SESSION_END);
   // OnBrowserRemoved does a ReleaseLater. When session end is received we exit
   // before the task runs resulting in this object not being deleted. This
   // Release balance out the Release scheduled by OnBrowserRemoved.
   Release();
 }
 
 bool TestingAutomationProvider::OnMessageReceived(
     const IPC::Message& message) {
+  base::ThreadRestrictions::ScopedAllowWait allow_wait;
   bool handled = true;
   bool deserialize_success = true;
   IPC_BEGIN_MESSAGE_MAP_EX(TestingAutomationProvider,
                            message,
                            deserialize_success)
     IPC_MESSAGE_HANDLER_DELAY_REPLY(AutomationMsg_CloseBrowser, CloseBrowser)
     IPC_MESSAGE_HANDLER(AutomationMsg_CloseBrowserRequestAsync,
                         CloseBrowserAsync)
     IPC_MESSAGE_HANDLER(AutomationMsg_ActivateTab, ActivateTab)
     IPC_MESSAGE_HANDLER_DELAY_REPLY(AutomationMsg_AppendTab, AppendTab)
@@ skipping 6677 matching lines @@
       *browser_handle = browser_tracker_->Add(browser);
       *success = true;
     }
   }
 }
 
 void TestingAutomationProvider::OnRemoveProvider() {
   if (g_browser_process)
     g_browser_process->GetAutomationProviderList()->RemoveProvider(this);
 }