blink: permissions: add plumbing to revoke permissions

Source/modules/permissions/Permissions.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 Permissions_h
 #define Permissions_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class ScriptState;
 class ScriptValue;
 class WebPermissionClient;
 
 class Permissions final
     : public GarbageCollected<Permissions>
     , public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     DEFINE_INLINE_TRACE() { }
 
     // TODO(mlamouri): Find better place for this. https://crbug.com/510948
     static WebPermissionClient* getClient(ExecutionContext*);
 
     ScriptPromise query(ScriptState*, const ScriptValue&);
+    ScriptPromise revoke(ScriptState*, const ScriptValue&);
 };
 
 } // namespace blink
 
 #endif // Permissions_h