Adds a field trial to control Web API kill switches.

chrome/browser/permissions/permission_context_base.h

 // Copyright 2014 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_BROWSER_PERMISSIONS_PERMISSION_CONTEXT_BASE_H_
 #define CHROME_BROWSER_PERMISSIONS_PERMISSION_CONTEXT_BASE_H_
 
 #include "base/callback.h"
 #include "base/containers/scoped_ptr_hash_map.h"
 #include "base/memory/ref_counted.h"
@@ skipping 109 matching lines @@
   // Store the decided permission as a content setting.
   // virtual since the permission might be stored with different restrictions
   // (for example for desktop notifications).
   virtual void UpdateContentSetting(const GURL& requesting_origin,
                                     const GURL& embedding_origin,
                                     ContentSetting content_setting);
 
   // Whether the permission should be restricted to secure origins.
   virtual bool IsRestrictedToSecureOrigins() const = 0;
 
+  // Whether the kill switch has been enabled for this API.
+  virtual bool IsApiKillSwitchOn() const;
+
  private:
   // Called when a bubble is no longer used so it can be cleaned up.
   void CleanUpBubble(const PermissionRequestID& id);
 
   Profile* profile_;
   const ContentSettingsType permission_type_;
   scoped_ptr<PermissionQueueController> permission_queue_controller_;
   base::ScopedPtrHashMap<std::string, scoped_ptr<PermissionBubbleRequest>>
       pending_bubbles_;
 
   // Must be the last member, to ensure that it will be
   // destroyed first, which will invalidate weak pointers
   base::WeakPtrFactory<PermissionContextBase> weak_factory_;
 };
 
 #endif  // CHROME_BROWSER_PERMISSIONS_PERMISSION_CONTEXT_BASE_H_