MD Settings: Refactor RoutableBehavior into MainPageBehavior

chrome/browser/resources/settings/settings_page/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': 'main_page_behavior',
       'dependencies': [
         '../compiled_resources2.gyp:route',
         'settings_section',
         'transition_behavior',
-        '<(EXTERNS_GYP):settings_private',
         '<(EXTERNS_GYP):web_animations',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:util',
       ],
       'includes': ['../../../../../third_party/closure_compiler/compile_js2.gypi'],
     },
     {
       'target_name': 'settings_animated_pages',
       'dependencies': [
         '../compiled_resources2.gyp:route',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:assert',
@@ skipping 35 matching lines @@
     {
       'target_name': 'transition_behavior',
       'dependencies': [
         '<(EXTERNS_GYP):settings_private',
         '<(EXTERNS_GYP):web_animations',
       ],
       'includes': ['../../../../../third_party/closure_compiler/compile_js2.gypi'],
     },
   ],
 }