aura: Unify WindowTreeHost for some platforms

ui/aura/aura.gyp

Index: ui/aura/aura.gyp
diff --git a/ui/aura/aura.gyp b/ui/aura/aura.gyp
index efaa46368ca11f50adfcaefda02822c41eb007a7..f18b8a57f9b541f34798ed5e0d3f5ba0e738a7d3 100644
--- a/ui/aura/aura.gyp
+++ b/ui/aura/aura.gyp
@@ -108,10 +108,6 @@
         'window_tree_host_mac.h',
         'window_tree_host_mac.mm',
         'window_tree_host_observer.h',
-        'window_tree_host_ozone.cc',
-        'window_tree_host_ozone.h',
-        'window_tree_host_win.cc',
-        'window_tree_host_win.h',
         'window_tree_host_x11.cc',
         'window_tree_host_x11.h',
       ],
@@ -142,6 +138,12 @@
             '../ozone/ozone.gyp:ozone_base',
           ],
         }],
+        ['OS=="win" or use_ozone==1', {

[mfomitchev, 2015/10/09 13:56:54]

The preferred way is to include the file in the main list and then exclude it
based on the condition rather than the other way around. This probably applies
to GN as well.
https://chromium.googlesource.com/external/gyp/+/master/docs/UserDocumentatio...

[mfomitchev, 2015/10/09 13:56:54]

Do you want to add android in a separate CL?

[no sievers, 2015/10/09 19:31:50]

Done.

[no sievers, 2015/10/09 19:31:50]

Well, might as well do it now that it's so straightforward. Done.

+          'sources': [
+            'window_tree_host_platform.cc',
+            'window_tree_host_platform.h',
+          ],
+        }],
       ],
     },
     {