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 080c7d57a5ef6fe040882b4f804107a9fc3eea0f..b8d7f9274a651b77f7f335306cb409ab8cbc0c88 100644
--- a/ui/gfx/BUILD.gn
+++ b/ui/gfx/BUILD.gn
@@ -78,6 +78,10 @@ component("gfx") {
     "display_change_notifier.h",
     "display_observer.cc",
     "display_observer.h",
+    "dpi.cc",
+    "dpi.h",
+    "dpi_linux.cc",
+    "dpi_win.cc",
     "favicon_size.cc",
     "favicon_size.h",
     "font.cc",
@@ -206,8 +210,6 @@ 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",
@@ -324,6 +326,11 @@ component("gfx") {
   if (is_linux) {
     configs += [ "//build/config/linux:fontconfig" ]
   }
+  if (!is_desktop_linux && !is_win) {
+    sources -= [
+      "dpi.cc",
+    ]
+  }
 
   # Ozone stuff.
   if (use_ozone) {