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 38 matching lines @@
 // It is mandatory to override IsRestrictedToSecureOrigin.
 // See midi_permission_context.h/cc or push_permission_context.cc/h for some
 // examples.
 
 class PermissionContextBase : public KeyedService {
  public:
   PermissionContextBase(Profile* profile,
                         const ContentSettingsType permission_type);
   ~PermissionContextBase() override;
 
+  // A field trial used to enable the global API kill switch.
+  static const char kApiKillSwitchFieldStudy[];
+
+  // The field trial param to enable the global API kill switch.
+  static const char kApiKillSwitchFieldParamBlockedValue[];

[mlamouri (slow - plz ping), 2015/10/20 13:35:45]

Could you have these two const char inside the .cc file instead of having them
static on the class?

[kcarattini, 2015/10/21 03:39:37]

They are here because they are used in the test as well. I also plan to add a
kill switch for camera/mic in another file.

+
   // The renderer is requesting permission to push messages.
   // When the answer to a permission request has been determined, |callback|
   // should be called with the result.
   virtual void RequestPermission(content::WebContents* web_contents,
                                  const PermissionRequestID& id,
                                  const GURL& requesting_frame,
                                  bool user_gesture,
                                  const BrowserPermissionCallback& callback);
 
   // Returns whether the permission has been granted, denied...
   virtual ContentSetting GetPermissionStatus(
       const GURL& requesting_origin,
       const GURL& embedding_origin) const;
 
   // Resets the permission to its default value.
   virtual void ResetPermission(const GURL& requesting_origin,
                                const GURL& embedding_origin);
 
   // Withdraw an existing permission request, no op if the permission request
   // was already cancelled by some other means.
   virtual void CancelPermissionRequest(content::WebContents* web_contents,
                                        const PermissionRequestID& id);
 
+  // Whether the kill switch has been enabled for this API.
+  virtual bool IsApiKillSwitchOn() const;

[mlamouri (slow - plz ping), 2015/10/20 13:35:45]

I don't think this needs to be virtual.

[Bernhard Bauer, 2015/10/20 14:27:17]

Add a comment that this method is public for testing? (Or make it protected and
friend the test class.)

[kcarattini, 2015/10/21 03:39:37]

Done.

[kcarattini, 2015/10/21 03:39:37]

Done.

+
  protected:
   // Decide whether the permission should be granted.
   // Calls PermissionDecided if permission can be decided non-interactively,
   // or NotifyPermissionSet if permission decided by presenting an infobar.
   virtual void DecidePermission(content::WebContents* web_contents,
                                 const PermissionRequestID& id,
                                 const GURL& requesting_origin,
                                 const GURL& embedding_origin,
                                 bool user_gesture,
                                 const BrowserPermissionCallback& callback);
@@ skipping 44 matching lines @@
   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_