ash: Add RootWindowHostFactory class.

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index b4d6be769892089eab98442a7e9ce44480fa5aee..74002935c308015c776b610d4a813402798eab33 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -81,6 +81,7 @@
         'display/display_error_dialog.h',
         'display/display_manager.cc',
         'display/display_manager.h',
+        'display/display_manager_delegate.h',
         'display/mouse_cursor_event_filter.cc',
         'display/mouse_cursor_event_filter.h',
         'display/output_configurator_animation.cc',
@@ -140,6 +141,9 @@
         'magnifier/partial_magnification_controller.h',
         'root_window_controller.cc',
         'root_window_controller.h',
+        'root_window_delegate.cc',
+        'root_window_delegate.h',
+        'root_window_delegate_win.cc',
         'rotator/screen_rotation.cc',
         'rotator/screen_rotation.h',
         'screen_ash.cc',
@@ -439,6 +443,11 @@
             ['exclude', 'accelerators/nested_dispatcher_controller.h'],
           ],
         }],
+        ['OS=="win"', {
+          'sources/': [
+            ['exclude', 'root_window_delegate.cc'],
+          ],
+        }],
         ['OS!="linux"', {
           'sources/': [
             ['exclude', 'system/monitor/tray_monitor.cc'],