Make chrome_shell_apk build

sync/sync_android.gypi

 # Copyright 2013 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.
 
 {
   'conditions': [
     ['OS == "android"', {
       'targets': [
         {
+          # GN: //sync/android:sync_java
           'target_name': 'sync_java',
           'type': 'none',
           'variables': {
             'java_in_dir': '../sync/android/java',
           },
           'dependencies': [
             '../base/base.gyp:base_java',
             '../base/base.gyp:base_java_test_support',
             '../net/net.gyp:net_java',
             '../third_party/cacheinvalidation/cacheinvalidation.gyp:cacheinvalidation_javalib',
             '../third_party/jsr-305/jsr-305.gyp:jsr_305_javalib',
           ],
           'includes': [ '../build/java.gypi' ],
         },
       ],
     }],
   ],
 }