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

content/browser/web_contents/web_contents_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/browser/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
@@ skipping 406 matching lines @@
       !command_line.HasSwitch(switches::kDisableRemoteFonts);
   prefs.xss_auditor_enabled =
       !command_line.HasSwitch(switches::kDisableXSSAuditor);
   prefs.application_cache_enabled =
       !command_line.HasSwitch(switches::kDisableApplicationCache);
 
   prefs.local_storage_enabled =
       !command_line.HasSwitch(switches::kDisableLocalStorage);
   prefs.databases_enabled =
       !command_line.HasSwitch(switches::kDisableDatabases);
+#if defined(OS_ANDROID)
+  prefs.webaudio_enabled =
+      command_line.HasSwitch(switches::kEnableWebAudio);
+#else
   prefs.webaudio_enabled =
       !command_line.HasSwitch(switches::kDisableWebAudio);
+#endif
 
   prefs.experimental_webgl_enabled =
       GpuProcessHost::gpu_enabled() &&
       !command_line.HasSwitch(switches::kDisable3DAPIs) &&
       !command_line.HasSwitch(switches::kDisableExperimentalWebGL);
 
   prefs.flash_3d_enabled =
       GpuProcessHost::gpu_enabled() &&
       !command_line.HasSwitch(switches::kDisableFlash3d);
   prefs.flash_stage3d_enabled =
@@ skipping 2648 matching lines @@
       browser_plugin_host()->embedder_render_process_host();
   *embedder_container_id = browser_plugin_host()->instance_id();
   int embedder_process_id =
       embedder_render_process_host ? embedder_render_process_host->GetID() : -1;
   if (embedder_process_id != -1) {
     *embedder_channel_name =
         StringPrintf("%d.r%d", render_view_host->GetProcess()->GetID(),
                      embedder_process_id);
   }
 }