[ScreenOrientation] Merge mojo interface ScreenOrientationListener into ScreenOrientation

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/renderer/render_thread_impl.h"
-
-namespace content {
-
-ScreenOrientationObserver::ScreenOrientationObserver() {
-}
-
-ScreenOrientationObserver::~ScreenOrientationObserver() {
-  StopIfObserving();
-}
-
-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() {
-  GetScreenOrientationListener()->Start();
-}
-
-void ScreenOrientationObserver::SendStopMessage() {
-  GetScreenOrientationListener()->Stop();
-}
-
-device::mojom::ScreenOrientationListener*
-ScreenOrientationObserver::GetScreenOrientationListener() {
-  if (!listener_) {
-    RenderThreadImpl::current()->GetChannel()->GetRemoteAssociatedInterface(
-        &listener_);
-  }
-  return listener_.get();
-}
-
-} // namespace content