Expose CHROMIUM_texture_mailbox/sync_point stubs in mojo public headers

mojo/mojo_apps.gypi

+# 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.
+
 {
   'targets': [
     {
       'target_name': 'mojo_js_lib',
       'type': 'static_library',
       'dependencies': [
         '../base/base.gyp:base',
         '../gin/gin.gyp:gin',
         '../ui/gl/gl.gyp:gl',
         '../v8/tools/gyp/v8.gyp:v8',
@@ skipping 82 matching lines @@
             'mojo_apps_js_unittests.isolate',
           ],
           'sources': [
             'mojo_apps_js_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }