[Chromecast] Turn CastContentWindow into an abstract interface.

chromecast/browser/android/cast_window_manager.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.
-
-#ifndef CHROMECAST_BROWSER_ANDROID_CAST_WINDOW_MANAGER_H_
-#define CHROMECAST_BROWSER_ANDROID_CAST_WINDOW_MANAGER_H_
-
-#include <jni.h>
-
-#include "base/android/jni_android.h"
-#include "base/android/scoped_java_ref.h"
-
-class CastWindowAndroid;
-
-namespace chromecast {
-namespace shell {
-
-// Given a CastWindowAndroid instance, creates and returns a Java wrapper.
-base::android::ScopedJavaLocalRef<jobject>
-CreateCastWindowView(CastWindowAndroid* shell);
-
-// Closes a previously created Java wrapper.
-void CloseCastWindowView(jobject shell_wrapper);
-
-// Registers the CastWindowManager native methods.
-bool RegisterCastWindowManager(JNIEnv* env);
-
-}  // namespace shell
-}  // namespace chromecast
-
-#endif  // CHROMECAST_BROWSER_ANDROID_CAST_WINDOW_MANAGER_H_