Re-land http://codereview.chromium.org/6339004 which was reverted

BUG=none
TEST=none
TBR=rniwa

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72278 0039d316-1c4b-4281-b951-d872f2087c98

chrome/app/generated_resources.grd

@@ -4009,6 +4009,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_FLAGS_ACCELERATED_CANVAS_2D_DESCRIPTION" desc="Description of the 'GPU Accelerated Canvas 2D' lab.">
         Enables higher performance of canvas tags with a 2D context by rendering using Graphics Processor Unit (GPU) hardware.
       </message>
+      <message name="IDS_FLAGS_WEBAUDIO_NAME" desc="Name of the 'Web Audio' lab.">
+        Web Audio
+      </message>
+      <message name="IDS_FLAGS_WEBAUDIO_DESCRIPTION" desc="Description of the 'Web Audio' lab.">
+        Enables the Web Audio API.
+      </message>
       <message name="IDS_FLAGS_WEBGL_NAME" desc="Name of the 'WebGL' lab.">
         WebGL
       </message>

chrome/browser/about_flags.cc

@@ -278,6 +278,13 @@ const Experiment kExperiments[] = {
     kOsAll,
     SINGLE_VALUE_TYPE(switches::kDisableInteractiveFormValidation)
   },
+  {
+    "webaudio",
+    IDS_FLAGS_WEBAUDIO_NAME,
+    IDS_FLAGS_WEBAUDIO_DESCRIPTION,
+    kOsMac,  // TODO(crogers): add windows and linux when FFT is ready.
+    SINGLE_VALUE_TYPE(switches::kEnableWebAudio)
+  },
 };
 
 const Experiment* experiments = kExperiments;

chrome/browser/tab_contents/render_view_host_delegate_helper.cc

@@ -273,6 +273,8 @@ WebPreferences RenderViewHostDelegateHelper::GetWebkitPrefs(
         !command_line.HasSwitch(switches::kDisableLocalStorage);
     web_prefs.databases_enabled =
         !command_line.HasSwitch(switches::kDisableDatabases);
+    web_prefs.webaudio_enabled =
+        command_line.HasSwitch(switches::kEnableWebAudio);
     web_prefs.experimental_webgl_enabled =
         gpu_enabled() &&
         !command_line.HasSwitch(switches::kDisable3DAPIs) &&

chrome/common/chrome_switches.cc

@@ -613,6 +613,9 @@ const char kEnableVideoLogging[]            = "enable-video-logging";
 // Order of the listed sub-arguments does not matter.
 const char kEnableWatchdog[]                = "enable-watchdog";
 
+// Enable web audio API.
+const char kEnableWebAudio[]                = "enable-webaudio";
+
 // Disable WebKit's XSSAuditor.  The XSSAuditor mitigates reflective XSS.
 const char kEnableXSSAuditor[]              = "enable-xss-auditor";
 

chrome/common/chrome_switches.h

@@ -182,6 +182,7 @@ extern const char kEnableVerticalTabs[];
 extern const char kEnableVideoFullscreen[];
 extern const char kEnableVideoLogging[];
 extern const char kEnableWatchdog[];
+extern const char kEnableWebAudio[];
 extern const char kEnableXSSAuditor[];
 // Experimental features.
 extern const char kExperimentalLocationFeatures[];

chrome/common/render_messages.cc

@@ -723,6 +723,7 @@ void ParamTraits<WebPreferences>::Write(Message* m, const param_type& p) {
   WriteParam(m, p.frame_flattening_enabled);
   WriteParam(m, p.allow_universal_access_from_file_urls);
   WriteParam(m, p.allow_file_access_from_file_urls);
+  WriteParam(m, p.webaudio_enabled);
   WriteParam(m, p.experimental_webgl_enabled);
   WriteParam(m, p.show_composited_layer_borders);
   WriteParam(m, p.accelerated_compositing_enabled);
@@ -777,6 +778,7 @@ bool ParamTraits<WebPreferences>::Read(const Message* m, void** iter,
       ReadParam(m, iter, &p->frame_flattening_enabled) &&
       ReadParam(m, iter, &p->allow_universal_access_from_file_urls) &&
       ReadParam(m, iter, &p->allow_file_access_from_file_urls) &&
+      ReadParam(m, iter, &p->webaudio_enabled) &&
       ReadParam(m, iter, &p->experimental_webgl_enabled) &&
       ReadParam(m, iter, &p->show_composited_layer_borders) &&
       ReadParam(m, iter, &p->accelerated_compositing_enabled) &&

chrome/renderer/render_thread.cc

@@ -937,6 +937,11 @@ void RenderThread::EnsureWebKitInitialized() {
   WebRuntimeFeatures::enableGeolocation(
       !command_line.HasSwitch(switches::kDisableGeolocation));
 
+#ifdef HAS_WEBAUDIO_RUNTIMEFEATURES
+  WebRuntimeFeatures::enableWebAudio(
+      command_line.HasSwitch(switches::kEnableWebAudio));
+#endif
+
   WebRuntimeFeatures::enableWebGL(
       !command_line.HasSwitch(switches::kDisable3DAPIs) &&
       !command_line.HasSwitch(switches::kDisableExperimentalWebGL));

webkit/glue/webpreferences.cc

@@ -60,6 +60,7 @@ WebPreferences::WebPreferences()
       frame_flattening_enabled(false),
       allow_universal_access_from_file_urls(false),
       allow_file_access_from_file_urls(false),
+      webaudio_enabled(false),
       experimental_webgl_enabled(false),
       show_composited_layer_borders(false),
       accelerated_compositing_enabled(false),
@@ -142,6 +143,11 @@ void WebPreferences::Apply(WebView* web_view) const {
   // but also because it cause a possible crash in Editor::hasBidiSelection().
   settings->setTextDirectionSubmenuInclusionBehaviorNeverIncluded();
 
+#ifdef HAS_WEBAUDIO_FEATURE_ENABLE
+  // Enable the web audio API if requested on the command line.
+  settings->setWebAudioEnabled(webaudio_enabled);
+#endif
+
   // Enable experimental WebGL support if requested on command line
   // and support is compiled in.
   bool enable_webgl =

webkit/glue/webpreferences.h

@@ -66,6 +66,7 @@ struct WebPreferences {
   bool frame_flattening_enabled;
   bool allow_universal_access_from_file_urls;
   bool allow_file_access_from_file_urls;
+  bool webaudio_enabled;
   bool experimental_webgl_enabled;
   bool show_composited_layer_borders;
   bool accelerated_compositing_enabled;