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

content/renderer/screen_orientation/screen_orientation_observer.cc

+// 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/renderer/screen_orientation/screen_orientation_observer.h"
+
+#include "content/common/screen_orientation_messages.h"
+
+namespace content {
+
+ScreenOrientationObserver::ScreenOrientationObserver() {
+}
+
+void ScreenOrientationObserver::Start(
+    blink::WebPlatformEventListener* listener) {
+  // This should never be called with a proper listener.
+  CHECK(listener == 0);
+  PlatformEventObserver<blink::WebPlatformEventListener>::Start(0);
+}
+
+void ScreenOrientationObserver::SendStartMessage() {
+  RenderThread::Get()->Send(new ScreenOrientationHostMsg_StartListening());
+}
+
+void ScreenOrientationObserver::SendStopMessage() {
+  RenderThread::Get()->Send(new ScreenOrientationHostMsg_StopListening());
+}
+
+} // namespace content