Tab audio mute control (views UI), behind a switch (off by default).

chrome/browser/ui/views/tabs/browser_tab_strip_controller.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/ui/views/tabs/browser_tab_strip_controller.h"
 
 #include "base/auto_reset.h"
 #include "base/prefs/pref_service.h"
 #include "base/task_runner_util.h"
 #include "base/threading/sequenced_worker_pool.h"
@@ skipping 282 matching lines @@
                                          CloseTabSource source) {
   // Cancel any pending tab transition.
   hover_tab_selector_.CancelTabTransition();
 
   tabstrip_->PrepareForCloseAt(model_index, source);
   model_->CloseWebContentsAt(model_index,
                              TabStripModel::CLOSE_USER_GESTURE |
                              TabStripModel::CLOSE_CREATE_HISTORICAL_TAB);
 }
 
+void BrowserTabStripController::ToggleTabAudioMute(int model_index) {
+  content::WebContents* const contents = model_->GetWebContentsAt(model_index);
+  chrome::SetTabAudioMuted(contents, !chrome::IsTabAudioMuted(contents));
+}
+
 void BrowserTabStripController::ShowContextMenuForTab(
     Tab* tab,
     const gfx::Point& p,
     ui::MenuSourceType source_type) {
   context_menu_contents_.reset(new TabContextMenuContents(tab, this));
   context_menu_contents_->RunMenuAt(p, source_type);
 }
 
 void BrowserTabStripController::UpdateLoadingAnimations() {
   // Don't use the model count here as it's possible for this to be invoked
@@ skipping 266 matching lines @@
       url,
       mime_type.empty() ||
       net::IsSupportedMimeType(mime_type) ||
       content::PluginService::GetInstance()->GetPluginInfo(
           -1,                // process ID
           MSG_ROUTING_NONE,  // routing ID
           model_->profile()->GetResourceContext(),
           url, GURL(), mime_type, false,
           NULL, &plugin, NULL));
 }