[Chromecast] Turn CastContentWindow into an abstract interface.

chromecast/browser/android/jni_registrar.cc

+// Copyright 2016 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 "chromecast/browser/android/jni_registrar.h"
+
+#include "chromecast/browser/android/cast_content_window_android.h"
+#include "chromecast/browser/android/cast_metrics_helper_android.h"
+#include "chromecast/browser/android/cast_web_contents_activity.h"
+
+namespace chromecast {
+namespace shell {
+
+bool RegisterJni(JNIEnv* env) {
+  if (!CastContentWindowAndroid::RegisterJni(env))
+    return false;
+  if (!CastMetricsHelperAndroid::RegisterJni(env))
+    return false;
+  if (!CastWebContentsActivity::RegisterJni(env))
+    return false;
+
+  return true;
+}
+
+}  // namespace shell
+}  // namespace chromecast