[Offline pages] Extract internals page interaction with browser to a proxy

chrome/browser/resources/offline_pages/compiled_resources2.gyp

 # Copyright 2016 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': 'offline_internals',
       'dependencies': [
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:assert',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:cr',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:load_time_data',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:util',
+        'offline_internals_browser_proxy',
       ],
       'includes': ['../../../../third_party/closure_compiler/compile_js2.gypi'],
     },
+    {
+      'target_name': 'offline_internals_browser_proxy',
+      'dependencies': [
+        '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:cr',
+      ],
+      'includes': ['../../../../third_party/closure_compiler/compile_js2.gypi'],
+    },
   ],
 }