disable web audio by default on android and add switches to enable it

content/renderer/render_thread_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.
 
 #include "content/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <vector>
@@ skipping 561 matching lines @@
 
   WebKit::WebRuntimeFeatures::enablePointerLock(
       !command_line.HasSwitch(switches::kDisablePointerLock));
 
   WebKit::WebRuntimeFeatures::enableVideoTrack(
       command_line.HasSwitch(switches::kEnableVideoTrack));
 
   WebKit::WebRuntimeFeatures::enableEncryptedMedia(
       command_line.HasSwitch(switches::kEnableEncryptedMedia));
 
+#if defined(OS_ANDROID)
+  WebRuntimeFeatures::enableWebAudio(
+      command_line.HasSwitch(switches::kEnableWebAudio) &&
+      media::IsMediaLibraryInitialized());
+#else
   WebRuntimeFeatures::enableWebAudio(
       !command_line.HasSwitch(switches::kDisableWebAudio) &&
       media::IsMediaLibraryInitialized());
+#endif
 
   WebRuntimeFeatures::enablePushState(true);
 
   WebRuntimeFeatures::enableTouch(
       command_line.HasSwitch(switches::kEnableTouchEvents));
 
   WebRuntimeFeatures::enableDeviceMotion(
       command_line.HasSwitch(switches::kEnableDeviceMotion));
 
   WebRuntimeFeatures::enableDeviceOrientation(
@@ skipping 460 matching lines @@
 
 scoped_refptr<base::MessageLoopProxy>
 RenderThreadImpl::GetFileThreadMessageLoopProxy() {
   DCHECK(message_loop() == MessageLoop::current());
   if (!file_thread_.get()) {
     file_thread_.reset(new base::Thread("Renderer::FILE"));
     file_thread_->Start();
   }
   return file_thread_->message_loop_proxy();
 }