Make Screen Orientation use Platform Events in order to handle polling.

Source/modules/screen_orientation/ScreenOrientationDispatcher.cpp

+// 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 "config.h"
+#include "modules/screen_orientation/ScreenOrientationDispatcher.h"
+
+#include "public/platform/Platform.h"
+
+namespace blink {
+
+ScreenOrientationDispatcher& ScreenOrientationDispatcher::instance()
+{
+    DEFINE_STATIC_LOCAL(ScreenOrientationDispatcher, screenOrientationDispatcher, ());
+    return screenOrientationDispatcher;
+}
+
+ScreenOrientationDispatcher::ScreenOrientationDispatcher()
+{
+}
+
+ScreenOrientationDispatcher::~ScreenOrientationDispatcher()
+{
+}
+
+void ScreenOrientationDispatcher::startListening()
+{
+    blink::Platform::current()->startListening(WebPlatformEventScreenOrientation, 0);
+}
+
+void ScreenOrientationDispatcher::stopListening()
+{
+    blink::Platform::current()->stopListening(WebPlatformEventScreenOrientation);
+}
+
+} // namespace blink