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

chrome/browser/about_flags.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 "chrome/browser/about_flags.h"
 
 #include <algorithm>
 #include <iterator>
 #include <map>
 #include <set>
@@ skipping 1943 matching lines @@
     kOsWin | kOsCrOS,
     SINGLE_VALUE_TYPE(switches::kEnableSavePasswordBubble)
   },
 #endif
   {
     "embed-flash-fullscreen",
     IDS_FLAGS_EMBED_FLASH_FULLSCREEN_NAME,
     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;
 size_t num_experiments = arraysize(kExperiments);
 
 // Stores and encapsulates the little state that about:flags has.
 class FlagsState {
  public:
   FlagsState() : needs_restart_(false) {}
   void ConvertFlagsToSwitches(FlagsStorage* flags_storage,
@@ skipping 491 matching lines @@
 }
 
 const Experiment* GetExperiments(size_t* count) {
   *count = num_experiments;
   return experiments;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags