Make mojo_system static and mojo_system_impl a component, never use both

content/content_app.gypi

 # Copyright (c) 2012 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.
 
 {
   'include_dirs': [
     '..',
   ],
   'dependencies': [
     '../base/base.gyp:base',
@@ skipping 51 matching lines @@
     ['OS=="ios"', {
       'sources!': [
         'app/content_main.cc',
         'app/mojo/mojo_init.cc',
         'app/mojo/mojo_init.h',
       ],
     }, {  # OS!="ios"
       'dependencies': [
         '../mojo/mojo.gyp:mojo_environment_chromium',
         '../mojo/mojo.gyp:mojo_service_manager',
-        '../mojo/mojo.gyp:mojo_system',
         '../mojo/mojo.gyp:mojo_system_impl',
      ],
     }],
   ],
 }