extensions: Check |enable_extensions| flag before depending on extension code.

chrome/chrome_browser_ui.gypi

 # Copyright 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.
 
 {
   'variables': {
     # There are two sections of sources:
     # * "Platform"-based sources (OS, toolkit, etc.)
     # * Feature/directory-based sources (e.g., history, printing)
 
@@ skipping 2894 matching lines @@
           ],
           'conditions': [
             ['chromeos == 0 and (OS!="mac" or mac_views_browser==1)', {
               'sources': [ '<@(chrome_browser_ui_views_non_chromeos_sources)' ],
             }],
             ['use_ash == 1', {
               'sources': [ '<@(chrome_browser_ui_ash_views_sources)' ],
             }],
             ['OS!="mac"', {
               'sources': [ '<@(chrome_browser_ui_views_non_mac_sources)' ],
-              'dependencies': [
-                '<(DEPTH)/extensions/components/extensions_components.gyp:native_app_window',
+              'conditions': [
+                ['enable_extensions==0', {
+                  'sources/': [
+                    ['exclude', '^browser/ui/views/extensions/'],
+                  ],
+                }, {
+                  'dependencies': [
+                    '<(DEPTH)/extensions/components/extensions_components.gyp:native_app_window',
+                  ],
+                }],
               ],
             }],
           ],
         }],
         ['use_aura==1 and chromeos==0 and use_ozone==0 and OS=="linux"', {
           'dependencies': [
             # gtk2 is the only component that can interact with gtk2 in our new
             # world.
             'browser/ui/libgtk2ui/libgtk2ui.gyp:gtk2ui',
             '../build/linux/system.gyp:gio',
@@ skipping 267 matching lines @@
           ],
           'sources': [
             '<@(chrome_browser_ui_non_mobile_sources)',
             '<@(chrome_browser_ui_omnibox_non_mobile_sources)',
           ],
         }],
       ],
     },
   ],
 }