WebMediaRecorder: adding abstract classes to public/platform

public/platform/WebMediaRecorderHandler.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 WebMediaRecorderHandler_h
+#define WebMediaRecorderHandler_h
+
+namespace blink {
+
+class WebMediaRecorderHandlerClient;
+class WebMediaStream;
+class WebString;
+
+class WebMediaRecorderHandler {
+public:
+    virtual ~WebMediaRecorderHandler() { }
+    virtual bool canSupportMimeType(const WebString& mimeType) = 0;
+    virtual bool initialize(WebMediaRecorderHandlerClient*,
+                            const WebMediaStream&,
+                            const WebString& mimeType) = 0;
+    virtual bool start() = 0;
+    virtual bool start(int timeslice) = 0;
+    virtual void stop() = 0;
+    virtual void pause() = 0;
+    virtual void resume() = 0;
+};
+
+} // namespace blink
+#endif