Allow Waitable event to be used to intentionally hang the UI thread for debugging purposes.

base/threading/thread_restrictions.h

 // 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.
 
 #ifndef BASE_THREADING_THREAD_RESTRICTIONS_H_
 #define BASE_THREADING_THREAD_RESTRICTIONS_H_
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 
@@ skipping 24 matching lines @@
 }
 namespace content {
 class BrowserGpuChannelHostFactory;
 class BrowserGpuMemoryBufferManager;
 class BrowserShutdownProfileDumper;
 class BrowserTestBase;
 class GpuChannelHost;
 class NestedMessagePumpAndroid;
 class RenderWidgetResizeHelper;
 class ScopedAllowWaitForAndroidLayoutTests;
+class ScopedAllowWaitForDebugURL;
 class TextInputClientMac;
 }  // namespace content
 namespace dbus {
 class Bus;
 }
 namespace disk_cache {
 class BackendImpl;
 class InFlightIO;
 }
 namespace mojo {
@@ skipping 113 matching lines @@
 #endif
 
  private:
   // DO NOT ADD ANY OTHER FRIEND STATEMENTS, talk to jam or brettw first.
   // BEGIN ALLOWED USAGE.
   friend class content::BrowserShutdownProfileDumper;
   friend class content::BrowserTestBase;
   friend class content::NestedMessagePumpAndroid;
   friend class content::RenderWidgetResizeHelper;
   friend class content::ScopedAllowWaitForAndroidLayoutTests;
+  friend class content::ScopedAllowWaitForDebugURL;
   friend class ::HistogramSynchronizer;
   friend class ::ScopedAllowWaitForLegacyWebViewApi;
   friend class cc::CompletionEvent;
   friend class cc::TaskGraphRunner;
   friend class mojo::common::WatcherThreadManager;
   friend class remoting::AutoThread;
   friend class MessagePumpDefault;
   friend class SequencedWorkerPool;
   friend class SimpleThread;
   friend class Thread;
@@ skipping 41 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowWait);
   };
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_RESTRICTIONS_H_