Add a flag to the compiler for compiling polymer code.

ui/webui/resources/cr_elements/v0_8/cr_checkbox/compiled_resources.gyp

 # 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': 'focus_manager',
-      'variables': {
-        'depends': [
-          '../../assert.js',
-          '../../cr.js',
-        ],
-      },
+      'target_name': 'cr_checkbox',
       'includes': ['../../../../../../third_party/closure_compiler/compile_js.gypi'],
-    },
+    }
   ],
 }