mash: Migrate popup_message to ash/common.

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index c352832cfa4d89b24d965f8a89315734f6ace121..e28f3d7e994a797240a9d60f573218d3f69ab43e 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -77,6 +77,8 @@
       'common/metrics/user_metrics_action.h',
       'common/multi_profile_uma.cc',
       'common/multi_profile_uma.h',
+      'common/popup_message.cc',
+      'common/popup_message.h',
       'common/root_window_controller_common.cc',
       'common/root_window_controller_common.h',
       'common/session/session_state_delegate.cc',
@@ -536,8 +538,6 @@
       'pointer_watcher_delegate.h',
       'pointer_watcher_delegate_aura.cc',
       'pointer_watcher_delegate_aura.h',
-      'popup_message.cc',
-      'popup_message.h',
       'root_window_controller.cc',
       'root_window_controller.h',
       'root_window_settings.cc',
@@ -897,6 +897,7 @@
       'autoclick/autoclick_unittest.cc',
       'common/display/display_info_unittest.cc',
       'common/material_design/material_design_controller_unittest.cc',
+      'common/popup_message_unittest.cc',
       'common/shelf/shelf_model_unittest.cc',
       'common/system/chromeos/power/power_status_unittest.cc',
       'common/system/chromeos/power/power_status_view_unittest.cc',
@@ -945,7 +946,6 @@
       'metrics/task_switch_metrics_recorder_unittest.cc',
       'metrics/task_switch_time_tracker_unittest.cc',
       'metrics/user_metrics_recorder_unittest.cc',
-      'popup_message_unittest.cc',
       'root_window_controller_unittest.cc',
       'rotator/screen_rotation_animation_unittest.cc',
       'screen_util_unittest.cc',