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

ui/gfx/BUILD.gn

Index: ui/gfx/BUILD.gn
diff --git a/ui/gfx/BUILD.gn b/ui/gfx/BUILD.gn
index ed3cc5685e38977f7755565669f690b3bd8a5cad..da9ca59197b6e2cea56f248814463cd97569af8b 100644
--- a/ui/gfx/BUILD.gn
+++ b/ui/gfx/BUILD.gn
@@ -78,6 +78,8 @@ component("gfx") {
     "display_change_notifier.h",
     "display_observer.cc",
     "display_observer.h",
+    "dpi.cc",
+    "dpi.h",
     "favicon_size.cc",
     "favicon_size.h",
     "font.cc",
@@ -206,8 +208,6 @@ component("gfx") {
     "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",
@@ -325,6 +325,11 @@ component("gfx") {
   if (is_linux) {
     configs += [ "//build/config/linux:fontconfig" ]
   }
+  if (!is_desktop_linux && !is_win) {
+    sources -= [
+      "dpi.cc",
+    ]
+  }
 
   # Ozone stuff.
   if (use_ozone) {