[Chromecast] Turn CastContentWindow into an abstract interface.

chromecast/browser/android/apk/src/org/chromium/chromecast/shell/CastMetricsHelper.java

 // Copyright 2015 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.
 
 package org.chromium.chromecast.shell;
 
 import org.chromium.base.annotations.JNINamespace;
 
 /**
  * Wrapper of native CastMetricsHelper.
  */
-@JNINamespace("chromecast")
+@JNINamespace("chromecast::shell")
 public final class CastMetricsHelper {
-
     public static void logMediaPlay() {
         nativeLogMediaPlay();
     }
     private static native void nativeLogMediaPlay();
 
     public static void logMediaPause() {
         nativeLogMediaPause();
     }
     private static native void nativeLogMediaPause();
 
 }