Remove WebPresentationClient and WebPresentationController.

public/platform/WebPresentationClient.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 WebPresentationClient_h
-#define WebPresentationClient_h
-
-namespace blink {
-
-class WebPresentationController;
-
-// The implementation the embedder has to provide for the Presentation API to work.
-class WebPresentationClient {
-public:
-    virtual ~WebPresentationClient() { }
-
-    // Passes the Blink-side delegate to the embedder.
-    virtual void setController(WebPresentationController*) = 0;
-
-    // Called when the frame attaches the first event listener to or removes the
-    // last event listener from the |availablechange| event.
-    virtual void updateAvailableChangeWatched(bool watched) = 0;
-};
-
-} // namespace blink
-
-#endif // WebPresentationClient_h