mash: Convert TrayBackgroundView to wm common types

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index 20435e85cde209672af9c860f28ad6cae9cba944..358bfc9758d89c182126f3a1088edc525f676fce 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -156,20 +156,28 @@
       'common/system/tray/hover_highlight_view.h',
       'common/system/tray/special_popup_row.cc',
       'common/system/tray/special_popup_row.h',
+      'common/system/tray/system_tray_bubble.cc',
+      'common/system/tray/system_tray_bubble.h',
       'common/system/tray/system_tray_delegate.cc',
       'common/system/tray/system_tray_delegate.h',
       'common/system/tray/system_tray_item.cc',
       'common/system/tray/system_tray_item.h',
       'common/system/tray/throbber_view.cc',
       'common/system/tray/throbber_view.h',
+      'common/system/tray/tray_background_view.cc',
+      'common/system/tray/tray_background_view.h',
       'common/system/tray/tray_bar_button_with_title.cc',
       'common/system/tray/tray_bar_button_with_title.h',
+      'common/system/tray/tray_bubble_wrapper.cc',
+      'common/system/tray/tray_bubble_wrapper.h',
       'common/system/tray/tray_constants.cc',
       'common/system/tray/tray_constants.h',
       'common/system/tray/tray_details_view.cc',
       'common/system/tray/tray_details_view.h',
       'common/system/tray/tray_empty.cc',
       'common/system/tray/tray_empty.h',
+      'common/system/tray/tray_event_filter.cc',
+      'common/system/tray/tray_event_filter.h',
       'common/system/tray/tray_image_item.cc',
       'common/system/tray/tray_image_item.h',
       'common/system/tray/tray_item_more.cc',
@@ -608,16 +616,8 @@
       'system/tray/media_security/multi_profile_media_tray_item.h',
       'system/tray/system_tray.cc',
       'system/tray/system_tray.h',
-      'system/tray/system_tray_bubble.cc',
-      'system/tray/system_tray_bubble.h',
       'system/tray/system_tray_notifier.cc',
       'system/tray/system_tray_notifier.h',
-      'system/tray/tray_background_view.cc',
-      'system/tray/tray_background_view.h',
-      'system/tray/tray_bubble_wrapper.cc',
-      'system/tray/tray_bubble_wrapper.h',
-      'system/tray/tray_event_filter.cc',
-      'system/tray/tray_event_filter.h',
       'system/user/button_from_view.cc',
       'system/user/button_from_view.h',
       'system/user/login_status.cc',