Removes some dead code

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")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
 
 # Historical note: Ash shipped on Windows for a couple years to support
@@ skipping 661 matching lines @@
     "first_run/first_run_helper_impl.h",
     "high_contrast/high_contrast_controller.cc",
     "high_contrast/high_contrast_controller.h",
     "host/ash_window_tree_host.cc",
     "host/ash_window_tree_host.h",
     "host/ash_window_tree_host_init_params.h",
     "host/ash_window_tree_host_platform.cc",
     "host/ash_window_tree_host_platform.h",
     "host/ash_window_tree_host_unified.cc",
     "host/ash_window_tree_host_unified.h",
-    "host/ash_window_tree_host_win.cc",
-    "host/ash_window_tree_host_win.h",
     "host/ash_window_tree_host_x11.cc",
     "host/ash_window_tree_host_x11.h",
     "host/root_window_transformer.h",
     "host/transformer_helper.cc",
     "host/transformer_helper.h",
     "ime/input_method_event_handler.cc",
     "ime/input_method_event_handler.h",
     "laser/laser_pointer_controller.cc",
     "laser/laser_pointer_controller.h",
     "laser/laser_pointer_points.cc",
@@ skipping 739 matching lines @@
     "//content/public/app:both",
     "//device/bluetooth",
   ]
 
   data_deps = [
     "//ash/common/strings:ash_test_strings",
     "//ash/resources:ash_test_resources_with_content_100_percent",
     "//ash/resources:ash_test_resources_200_percent",
   ]
 }