Enable hidpi on Linux, refactor a bit on Windows to share

ui/base/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/ui.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 }
@@ skipping 220 matching lines @@
     "view_prop.cc",
     "view_prop.h",
     "webui/jstemplate_builder.cc",
     "webui/jstemplate_builder.h",
     "webui/web_ui_util.cc",
     "webui/web_ui_util.h",
     "win/accessibility_ids_win.h",
     "win/accessibility_misc_utils.cc",
     "win/accessibility_misc_utils.h",
     "win/atl_module.h",
-    "win/dpi_setup.cc",
-    "win/dpi_setup.h",
     "win/foreground_helper.cc",
     "win/foreground_helper.h",
     "win/hidden_window.cc",
     "win/hidden_window.h",
     "win/hwnd_subclass.cc",
     "win/hwnd_subclass.h",
     "win/internal_constants.cc",
     "win/internal_constants.h",
     "win/lock_state.cc",
     "win/lock_state.h",
@@ skipping 643 matching lines @@
     deps += [
       "//chromeos",
       "//ui/aura:test_support",
       "//ui/events:gesture_detection",
       "//ui/chromeos:ui_chromeos",
     ]
   }
 }
 }
 # TODO(GYP) Mac (ui_unittest_bundle) and Android (ui_unittests_apk).