Add a flag to enable impl-thread event handling on Mac

content/browser/renderer_host/render_process_host_impl.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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 1218 matching lines @@
     switches::kDisableWebRTC,
     switches::kEnableSpeechRecognition,
     switches::kMediaDrmEnableNonCompositing,
     switches::kNetworkCountryIso,
     switches::kDisableWebAudio,
     switches::kRendererWaitForJavaDebugger,
 #endif
 #if defined(OS_MACOSX)
     // Allow this to be set when invoking the browser and relayed along.
     switches::kEnableSandboxLogging,
+    switches::kEnableThreadedEventHandlingMac,
 #endif
 #if defined(OS_WIN)
     switches::kDisableDirectWrite,
 #endif
 #if defined(OS_CHROMEOS)
     switches::kDisableVaapiAcceleratedVideoEncode,
 #endif
   };
   renderer_cmd->CopySwitchesFrom(browser_cmd, kSwitchNames,
                                  arraysize(kSwitchNames));
@@ skipping 981 matching lines @@
 
 void RenderProcessHostImpl::DecrementWorkerRefCount() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK_GT(worker_ref_count_, 0);
   --worker_ref_count_;
   if (worker_ref_count_ == 0)
     Cleanup();
 }
 
 }  // namespace content