ash-enable-system-sounds is exposed to about:flags.

BUG=322820
TEST=manual tests on Daisy

Review URL: https://codereview.chromium.org/139323002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245256 0039d316-1c4b-4281-b951-d872f2087c98

chrome/app/chromeos_strings.grdp

@@ -4013,5 +4013,10 @@ Battery full
   <message name="IDS_CHARGER_REPLACEMENT_DIALOG_TITLE" desc="Title of the charger replacement UI dialg">
     Check charger
   </message>
-
+  <message name="IDS_FLAGS_ENABLE_SYSTEM_SOUNDS_NAME" desc="Name of the flag to enable system sounds independently from ChromeVox.">
+    Enable system sounds
+  </message>
+  <message name="IDS_FLAGS_ENABLE_SYSTEM_SOUNDS_DESCRIPTION" desc="Description of the flag to enable system sounds independently from ChromeVox.">
+    System sounds will be played independently from ChromeVox.
+  </message>
 </grit-part>

chrome/browser/about_flags.cc

@@ -1970,7 +1970,16 @@ const Experiment kExperiments[] = {
     IDS_FLAGS_EMBED_FLASH_FULLSCREEN_DESCRIPTION,
     kOsDesktop,
     SINGLE_VALUE_TYPE(switches::kEmbedFlashFullscreen)
+  },
+#if defined(USE_ASH) && defined(OS_CHROMEOS)
+  {
+    "enable-system-sounds",
+    IDS_FLAGS_ENABLE_SYSTEM_SOUNDS_NAME,
+    IDS_FLAGS_ENABLE_SYSTEM_SOUNDS_DESCRIPTION,
+    kOsCrOS,
+    SINGLE_VALUE_TYPE(ash::switches::kAshEnableSystemSounds)
   }
+#endif
 };
 
 const Experiment* experiments = kExperiments;