Componentize component_updater: Split crx_file code off into its own component.

components/crx_file.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': 'language_usage_metrics',
+      'target_name': 'crx_file',
       'type': 'static_library',
       'dependencies': [
         '../base/base.gyp:base',
       ],
       'include_dirs': [
         '..',
       ],
+      'defines': [
+        'CRX_FILE_IMPLEMENTATION',
+      ],
       'sources': [
-        'language_usage_metrics/language_usage_metrics.cc',
-        'language_usage_metrics/language_usage_metrics.h',
+        'crx_file/constants.h',
+        'crx_file/crx_file.cc',
+        'crx_file/crx_file.h',
       ],
     },
   ],
 }