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

ui/gfx/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 60 matching lines @@
     "color_profile_mac.mm",
     "color_profile_win.cc",
     "color_utils.cc",
     "color_utils.h",
     "display.cc",
     "display.h",
     "display_change_notifier.cc",
     "display_change_notifier.h",
     "display_observer.cc",
     "display_observer.h",
+    "dpi.cc",
+    "dpi.h",
     "favicon_size.cc",
     "favicon_size.h",
     "font.cc",
     "font.h",
     "font_fallback.h",
     "font_fallback_linux.cc",
     "font_fallback_mac.cc",
     "font_fallback_win.cc",
     "font_fallback_win.h",
     "font_list.cc",
@@ skipping 108 matching lines @@
     "transform.cc",
     "transform.h",
     "transform_util.cc",
     "transform_util.h",
     "ui_gfx_exports.cc",
     "utf16_indexing.cc",
     "utf16_indexing.h",
     "vsync_provider.h",
     "win/direct_write.cc",
     "win/direct_write.h",
-    "win/dpi.cc",
-    "win/dpi.h",
     "win/hwnd_util.cc",
     "win/hwnd_util.h",
     "win/scoped_set_map_mode.h",
     "win/singleton_hwnd.cc",
     "win/singleton_hwnd.h",
     "win/window_impl.cc",
     "win/window_impl.h",
   ]
 
   defines = [ "GFX_IMPLEMENTATION" ]
@@ skipping 343 matching lines @@
 if (is_android) {
   generate_jni("gfx_jni_headers") {
     sources = [
       "../android/java/src/org/chromium/ui/gfx/BitmapHelper.java",
       "../android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java",
       "../android/java/src/org/chromium/ui/gfx/ViewConfigurationHelper.java",
     ]
     jni_package = "gfx"
   }
 }