Create separate extensions_common and extensions_browser GYP targets.

chrome/chrome_browser_extensions.gypi

 # Copyright (c) 2013 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': 'browser_extensions',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 10 matching lines @@
         'chrome_resources.gyp:theme_resources',
         'common',
         'common/extensions/api/api.gyp:api',
         'common_net',
         'debugger',
         'in_memory_url_index_cache_proto',
         'installer_util',
         '../content/content.gyp:content_browser',
         '../crypto/crypto.gyp:crypto',
         '../device/bluetooth/bluetooth.gyp:device_bluetooth',
+        '../extensions/extensions.gyp:extensions_browser',
         '../net/net.gyp:net',
         '../skia/skia.gyp:skia',
         '../sync/sync.gyp:sync',
         '../third_party/cacheinvalidation/cacheinvalidation.gyp:cacheinvalidation',
         '../third_party/icu/icu.gyp:icui18n',
         '../third_party/icu/icu.gyp:icuuc',
         '../third_party/leveldatabase/leveldatabase.gyp:leveldatabase',
         '../third_party/libusb/libusb.gyp:libusb',
         '../third_party/re2/re2.gyp:re2',
         '../third_party/webrtc/modules/modules.gyp:desktop_capture',
         '../ui/base/strings/ui_strings.gyp:ui_strings',
         '../ui/ui.gyp:ui',
         '../ui/ui.gyp:ui_resources',
         '../url/url.gyp:url_lib',
         '../webkit/common/user_agent/webkit_user_agent.gyp:user_agent',
         '../webkit/storage_browser.gyp:webkit_storage_browser',
         '../webkit/storage_common.gyp:webkit_storage_common',
         '../webkit/webkit_resources.gyp:webkit_resources',
       ],
       'include_dirs': [
         '..',
         '<(INTERMEDIATE_DIR)',
       ],
       'sources': [
         # All .cc, .h, .m, and .mm files under browser/extensions except for
         # tests and mocks.
-        '../extensions/browser/extension_prefs_scope.h',
-        '../extensions/browser/extension_error.cc',
-        '../extensions/browser/extension_error.h',
-        '../extensions/browser/file_highlighter.cc',
-        '../extensions/browser/file_highlighter.h',
-        '../extensions/browser/file_reader.cc',
-        '../extensions/browser/file_reader.h',
-        '../extensions/browser/pref_names.cc',
-        '../extensions/browser/pref_names.h',
-        '../extensions/browser/view_type_utils.cc',
-        '../extensions/browser/view_type_utils.h',
         'browser/apps/app_url_redirector.cc',
         'browser/apps/app_url_redirector.h',
         'browser/apps/chrome_apps_client.cc',
         'browser/apps/chrome_apps_client.h',
         'browser/apps/shortcut_manager.cc',
         'browser/apps/shortcut_manager.h',
         'browser/apps/shortcut_manager_factory.cc',
         'browser/apps/shortcut_manager_factory.h',
         'browser/extensions/active_tab_permission_granter.cc',
         'browser/extensions/active_tab_permission_granter.h',
@@ skipping 1034 matching lines @@
           'variables': {
             'proto_in_dir': 'browser/chromeos/contacts',
             'proto_out_dir': 'chrome/browser/chromeos/contacts',
           },
           'includes': [ '../build/protoc.gypi' ]
         },
       ],
     },],  # 'chromeos=1'
   ],  # 'conditions'
 }