mash: Migrate ShelfButton* to wm common types

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index cce92e6487956ffb60fe35ad724b38a63ec71562..cf83f50da14500b495791262e0497698202ea92b 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -108,6 +108,10 @@
       'common/shelf/overflow_button.h',
       'common/shelf/shelf_alignment_menu.cc',
       'common/shelf/shelf_alignment_menu.h',
+      'common/shelf/shelf_button.cc',
+      'common/shelf/shelf_button.h',
+      'common/shelf/shelf_button_pressed_metric_tracker.cc',
+      'common/shelf/shelf_button_pressed_metric_tracker.h',
       'common/shelf/shelf_constants.cc',
       'common/shelf/shelf_constants.h',
       'common/shelf/shelf_delegate.h',
@@ -622,10 +626,6 @@
       'shelf/shelf.h',
       'shelf/shelf_bezel_event_filter.cc',
       'shelf/shelf_bezel_event_filter.h',
-      'shelf/shelf_button.cc',
-      'shelf/shelf_button.h',
-      'shelf/shelf_button_pressed_metric_tracker.cc',
-      'shelf/shelf_button_pressed_metric_tracker.h',
       'shelf/shelf_icon_observer.h',
       'shelf/shelf_layout_manager.cc',
       'shelf/shelf_layout_manager.h',
@@ -913,6 +913,7 @@
       'common/display/display_info_unittest.cc',
       'common/material_design/material_design_controller_unittest.cc',
       'common/popup_message_unittest.cc',
+      'common/shelf/shelf_button_pressed_metric_tracker_unittest.cc',
       'common/shelf/shelf_locking_manager_unittest.cc',
       'common/shelf/shelf_model_unittest.cc',
       'common/shelf/shelf_navigator_unittest.cc',
@@ -973,7 +974,6 @@
       'root_window_controller_unittest.cc',
       'rotator/screen_rotation_animation_unittest.cc',
       'screen_util_unittest.cc',
-      'shelf/shelf_button_pressed_metric_tracker_unittest.cc',
       'shelf/shelf_layout_manager_unittest.cc',
       'shelf/shelf_tooltip_manager_unittest.cc',
       'shelf/shelf_unittest.cc',