Fix enable_cardboard/enable_cast for GN build of remoting/android.

remoting/android/client_java_tmpl.gni

 # 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.
 
 import("//build/config/android/rules.gni")
 import("//remoting/remoting_options.gni")
 
 template("remoting_android_client_java_tmpl") {
   android_library(target_name) {
     DEPRECATED_java_in_dir = "//remoting/android/java/src"
     java_files = []
 
-    if (enable_cast) {
+    if (remoting_enable_cast) {
       java_files += [ "//remoting/android/cast/src/org/chromium/chromoting/CastExtensionHandler.java" ]
     }
 
     deps = [
       "//base:base_java",
       "//remoting/android:remoting_android_client_java_resources",
       "//third_party/android_tools:android_support_v13_java",
       "//third_party/android_tools:android_support_v7_appcompat_java",
       "//third_party/android_tools:android_support_v7_mediarouter_java",
       "//third_party/cardboard-java",
       "//ui/android:ui_java",
     ]
 
     deps += [ invoker.remoting_google_play_services_library ]
   }
 }