Add chrome/browser/apps/BUILD.gn and move Chrome-specific code there

chrome/browser/extensions/BUILD.gn

 # 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
 import("//extensions/features/features.gni")
 import("//media/media_options.gni")
 import("//rlz/features/features.gni")
 
 assert(enable_extensions)
 
 static_library("extensions") {
   sources = [
     # TODO These references to files in //chrome/browser/ should either be
     # moved to the browser target or the files moved to this directory.
-    "../apps/app_launch_for_metro_restart_win.cc",
-    "../apps/app_launch_for_metro_restart_win.h",
-    "../apps/app_url_redirector.cc",
-    "../apps/app_url_redirector.h",
-    "../apps/app_window_registry_util.cc",
-    "../apps/app_window_registry_util.h",
-    "../apps/install_chrome_app.cc",
-    "../apps/install_chrome_app.h",
-    "../apps/shortcut_manager.cc",
-    "../apps/shortcut_manager.h",
-    "../apps/shortcut_manager_factory.cc",
-    "../apps/shortcut_manager_factory.h",
     "../ui/app_icon_loader.cc",
     "../ui/app_icon_loader.h",
     "../ui/toolbar/toolbar_actions_model.cc",
     "../ui/toolbar/toolbar_actions_model.h",
     "../ui/toolbar/toolbar_actions_model_factory.cc",
     "../ui/toolbar/toolbar_actions_model_factory.h",
     "../web_applications/update_shortcut_worker_win.cc",
     "../web_applications/update_shortcut_worker_win.h",
     "../web_applications/web_app.cc",
     "../web_applications/web_app.h",
@@ skipping 768 matching lines @@
   # we must omit the dependency from browser_extensions to browser.
   # However, this means browser_extensions and browser should more or less
   # have the same dependencies. Once browser_extensions is untangled from
   # browser, then we can clean up these dependencies.
   public_deps = [
     "//chrome/common/extensions/api",
     "//components/safe_browsing_db:util",
     "//content/public/browser",
   ]
   deps = [
+    "//apps",
     "//chrome:extra_resources",
     "//chrome:resources",
     "//chrome:strings",
     "//chrome/app:command_ids",
     "//chrome/app/resources:platform_locale_settings",
     "//chrome/app/theme:chrome_unscaled_resources",
     "//chrome/app/theme:theme_resources",
     "//chrome/app/vector_icons",
     "//chrome/browser/devtools",
     "//chrome/browser/media/router/discovery",
@@ skipping 362 matching lines @@
       "api/braille_display_private/brlapi_connection.cc",
       "api/braille_display_private/brlapi_connection.h",
       "api/braille_display_private/brlapi_keycode_map.cc",
       "api/braille_display_private/brlapi_keycode_map.h",
     ]
     deps += [ "//build/linux/libbrlapi" ]
   } else {
     sources += [ "api/braille_display_private/braille_controller_stub.cc" ]
   }
 }