Refactor "options" argument to getUserMedia to be a dictionary

Source/modules/mediastream/MediaDevices.h

 // Copyright 2015 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 MediaDevices_h
 #define MediaDevices_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 
 namespace blink {
 
-class Dictionary;
+class MediaStreamConstraints;
 class ScriptState;
 
 class MediaDevices final : public GarbageCollected<MediaDevices>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static MediaDevices* create()
     {
         return new MediaDevices();
     }
 
     ScriptPromise enumerateDevices(ScriptState*);
-    ScriptPromise getUserMedia(ScriptState*, const Dictionary&, ExceptionState&);
+    ScriptPromise getUserMedia(ScriptState*, const MediaStreamConstraints&, ExceptionState&);
     DEFINE_INLINE_TRACE() { }
 
 private:
     MediaDevices() { }
 };
 
 } // namespace blink
 
 #endif