mash: Move ShelfWindowWatcher[ItemDelegate] to ash/common.

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index 1c6b1c8fc2753c9a16b727ab93cf35801eb8beda..f1c2475ab66b93f7f67049b9d66744a98ceb47a6 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -134,6 +134,10 @@
       'common/shelf/shelf_tooltip_manager.cc',
       'common/shelf/shelf_tooltip_manager.h',
       'common/shelf/shelf_types.h',
+      'common/shelf/shelf_window_watcher.cc',
+      'common/shelf/shelf_window_watcher.h',
+      'common/shelf/shelf_window_watcher_item_delegate.cc',
+      'common/shelf/shelf_window_watcher_item_delegate.h',
       'common/shelf/wm_shelf.h',
       'common/shelf/wm_shelf_observer.h',
       'common/shelf/wm_shelf_util.cc',
@@ -643,10 +647,6 @@
       'shelf/shelf_view.h',
       'shelf/shelf_widget.cc',
       'shelf/shelf_widget.h',
-      'shelf/shelf_window_watcher.cc',
-      'shelf/shelf_window_watcher.h',
-      'shelf/shelf_window_watcher_item_delegate.cc',
-      'shelf/shelf_window_watcher_item_delegate.h',
       'shell.cc',
       'shell.h',
       'shell_init_params.cc',
@@ -923,6 +923,7 @@
       'common/shelf/shelf_model_unittest.cc',
       'common/shelf/shelf_navigator_unittest.cc',
       'common/shelf/shelf_tooltip_manager_unittest.cc',
+      'common/shelf/shelf_window_watcher_unittest.cc',
       'common/system/chromeos/brightness/tray_brightness_unittest.cc',
       'common/system/chromeos/ime_menu/ime_menu_tray_unittest.cc',
       'common/system/chromeos/media_security/multi_profile_media_tray_item_unittest.cc',
@@ -984,7 +985,6 @@
       'shelf/shelf_unittest.cc',
       'shelf/shelf_view_unittest.cc',
       'shelf/shelf_widget_unittest.cc',
-      'shelf/shelf_window_watcher_unittest.cc',
       'shell_unittest.cc',
       'sticky_keys/sticky_keys_overlay_unittest.cc',
       'sticky_keys/sticky_keys_unittest.cc',