1 // Copyright 2014 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "content/public/renderer/platform_event_observer.h" 6 7 namespace content { 8 9 // ScreenOrientationObserver is a helper class implementing the 10 // PlatformEventObserver template with blink::WebPlatformEventListener, which is 11 // a pure virtual class because it doesn't expect listeners. 12 // It is implemented on top of PlatformEventObserver to make sure it follows a 13 // common code path even though it only uses part of this code path: it is not 14 // expected to receive messages back but should send messages to start/stop 15 // listening. 16 // The intent of this class is to make sure that platforms that can't listen for 17 // display rotations at a marginal cost can be told when to actually do it. 18 class ScreenOrientationObserver 19 : public PlatformEventObserver<blink::WebPlatformEventListener> { 20 public: 21 ScreenOrientationObserver(); 22 23 // Overriding this method just to make sure |listener| is always null. 24 virtual void Start(blink::WebPlatformEventListener* listener) OVERRIDE; 25 26 protected: 27 virtual void SendStartMessage() OVERRIDE; 28 virtual void SendStopMessage() OVERRIDE; 29 }; 30 31 }; // namespace content 32
