mash: Move shelf_navigator.* to //ash/common/shelf

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index a812c1fa0eee890cc15b549179c5ed1b3ba08e65..2995bd9a93fc1f93769c3accc7cd2d7877193007 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -113,6 +113,8 @@
       'common/shelf/shelf_model.cc',
       'common/shelf/shelf_model.h',
       'common/shelf/shelf_model_observer.h',
+      'common/shelf/shelf_navigator.cc',
+      'common/shelf/shelf_navigator.h',
       'common/shelf/shelf_types.h',
       'common/shelf/wm_shelf.h',
       'common/shelf/wm_shelf_observer.h',
@@ -620,8 +622,6 @@
       'shelf/shelf_layout_manager_observer.h',
       'shelf/shelf_locking_manager.cc',
       'shelf/shelf_locking_manager.h',
-      'shelf/shelf_navigator.cc',
-      'shelf/shelf_navigator.h',
       'shelf/shelf_tooltip_manager.cc',
       'shelf/shelf_tooltip_manager.h',
       'shelf/shelf_util.cc',
@@ -909,6 +909,7 @@
       'common/material_design/material_design_controller_unittest.cc',
       'common/popup_message_unittest.cc',
       'common/shelf/shelf_model_unittest.cc',
+      'common/shelf/shelf_navigator_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',
@@ -969,7 +970,6 @@
       'shelf/shelf_button_pressed_metric_tracker_unittest.cc',
       'shelf/shelf_layout_manager_unittest.cc',
       'shelf/shelf_locking_manager_unittest.cc',
-      'shelf/shelf_navigator_unittest.cc',
       'shelf/shelf_tooltip_manager_unittest.cc',
       'shelf/shelf_unittest.cc',
       'shelf/shelf_view_unittest.cc',