Add GN files for src/win8.

ash/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")
 
 gypi_values = exec_script("//build/gypi_to_gn.py",
                           [ rebase_path("ash.gyp") ],
                           "scope",
@@ skipping 162 matching lines @@
     "//ui/views:test_support",
   ]
 
   if (is_win) {
     sources += [
       "test/test_metro_viewer_process_host.cc",
       "test/test_metro_viewer_process_host.h",
     ]
     deps += [
       "//ipc",
-      #'../ui/metro_viewer/metro_viewer.gyp:metro_viewer_messages',  TODO(GYP)
-      #'../win8/win8.gyp:metro_viewer',  TODO(GYP)
-      #'../win8/win8.gyp:test_support_win8',  TODO(GYP)
-      #'../win8/win8_tests.gyp:test_registrar',  TODO(GYP)
+      "//ui/metro_viewer",

[Slava Chigrin, 2014/12/23 12:40:18]

Seems, this target already added to the GN build. See 
https://code.google.com/p/chromium/codesearch#chromium/src/ui/metro_viewer/BU...

+      "//win8:metro_viewer",
+      "//win8:test_support_win8",
+      "//win8:test_registrar",
     ]
   }
 }
 
 static_library("ash_shell_lib") {
   testonly = true
   sources = gypi_values.ash_shell_lib_sources
 
   deps = [
     ":ash",
@@ skipping 171 matching lines @@
     "//content/test:test_support",
     "//skia",
     "//testing/gtest",
     "//ui/accessibility",
   ]
 
   if (is_chromeos) {
     deps += [ "//ui/display" ]
   }
 }