Add options for audio/video autoplay to chrome://settings/content.

chrome/renderer/content_settings_observer.h

 // 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.
 
 #ifndef CHROME_RENDERER_CONTENT_SETTINGS_OBSERVER_H_
 #define CHROME_RENDERER_CONTENT_SETTINGS_OBSERVER_H_
 
 #include <map>
 #include <set>
 
@@ skipping 49 matching lines @@
   // blink::WebContentSettingsClient implementation.
   bool allowDatabase(const blink::WebString& name,
                      const blink::WebString& display_name,
                      unsigned long estimated_size) override;
   void requestFileSystemAccessAsync(
       const blink::WebContentSettingCallbacks& callbacks) override;
   bool allowImage(bool enabled_per_settings,
                   const blink::WebURL& image_url) override;
   bool allowIndexedDB(const blink::WebString& name,
                       const blink::WebSecurityOrigin& origin) override;
+  bool allowMediaAutoplay(bool hidden) override;
   bool allowPlugins(bool enabled_per_settings) override;
   bool allowScript(bool enabled_per_settings) override;
   bool allowScriptFromSource(bool enabled_per_settings,
                              const blink::WebURL& script_url) override;
   bool allowStorage(bool local) override;
   bool allowReadFromClipboard(bool default_value) override;
   bool allowWriteToClipboard(bool default_value) override;
   bool allowMutationEvents(bool default_value) override;
   void didNotAllowPlugins() override;
   void didNotAllowScript() override;
@@ skipping 81 matching lines @@
   typedef std::map<int, blink::WebContentSettingCallbacks> PermissionRequestMap;
   PermissionRequestMap permission_requests_;
 
   // If true, IsWhitelistedForContentSettings will always return true.
   const bool should_whitelist_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentSettingsObserver);
 };
 
 #endif  // CHROME_RENDERER_CONTENT_SETTINGS_OBSERVER_H_