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

ui/gfx/gfx.gyp

Index: ui/gfx/gfx.gyp
diff --git a/ui/gfx/gfx.gyp b/ui/gfx/gfx.gyp
index 080ce32b3835ef78985e6159faa9c67784efd69f..e63bf769d4704a34c1b0739323f82d4e6a89c2b1 100644
--- a/ui/gfx/gfx.gyp
+++ b/ui/gfx/gfx.gyp
@@ -155,6 +155,10 @@
         'display_change_notifier.h',
         'display_observer.cc',
         'display_observer.h',
+        'dpi.cc',
+        'dpi.h',
+        'dpi_linux.cc',

[sky, 2014/10/22 21:11:18]

I suspect dpi_linux should not be present on chromeos.

[scottmg, 2014/10/22 23:56:18]

Done.

+        'dpi_win.cc',
         'favicon_size.cc',
         'favicon_size.h',
         'font.cc',
@@ -298,8 +302,6 @@
         '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',
@@ -415,6 +417,11 @@
             '<(DEPTH)/build/linux/system.gyp:fontconfig',
           ],
         }],
+        ['desktop_linux!=1 and OS!="win"', {
+          'sources!': [
+            'dpi.cc',
+          ],
+        }],
       ],
       'target_conditions': [
         # Need 'target_conditions' to override default filename_rules to include