Revert "Refactor code listening to platform events in content/renderer/."

content/renderer/screen_orientation/screen_orientation_observer.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.
-
-#include "content/public/renderer/platform_event_observer.h"
-
-namespace content {
-
-// ScreenOrientationObserver is a helper class implementing the
-// PlatformEventObserver template with blink::WebPlatformEventListener, which is
-// a pure virtual class because it doesn't expect listeners.
-// It is implemented on top of PlatformEventObserver to make sure it follows a
-// common code path even though it only uses part of this code path: it is not
-// expected to receive messages back but should send messages to start/stop
-// listening.
-// The intent of this class is to make sure that platforms that can't listen for
-// display rotations at a marginal cost can be told when to actually do it.
-class ScreenOrientationObserver
-    : public PlatformEventObserver<blink::WebPlatformEventListener> {
- public:
-  ScreenOrientationObserver();
-
-  // Overriding this method just to make sure |listener| is always null.
-  virtual void Start(blink::WebPlatformEventListener* listener) OVERRIDE;
-
- protected:
-  virtual void SendStartMessage() OVERRIDE;
-  virtual void SendStopMessage() OVERRIDE;
-};
-
-}; // namespace content