Replaced BackgroundAnimator with ShelfBackgroundAnimator.

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index 290b55a2c839c1874855a879372a1428b7073182..cd33639d3d597a0c70acc8df0b0d184e7a565397 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -108,6 +108,9 @@
       'common/shelf/overflow_button.h',
       'common/shelf/shelf_alignment_menu.cc',
       'common/shelf/shelf_alignment_menu.h',
+      'common/shelf/shelf_background_animator.cc',
+      'common/shelf/shelf_background_animator.h',
+      'common/shelf/shelf_background_animator_observer.h',
       'common/shelf/shelf_button.cc',
       'common/shelf/shelf_button.h',
       'common/shelf/shelf_button_pressed_metric_tracker.cc',
@@ -792,6 +795,8 @@
       'content/shell_content_state.h',
     ],
     'ash_test_support_sources': [
+      'common/test/material_design_controller_test_api.cc',
+      'common/test/material_design_controller_test_api.h',
       'common/test/test_volume_control_delegate.cc',
       'common/test/test_volume_control_delegate.h',
       'desktop_background/desktop_background_controller_test_api.cc',
@@ -812,8 +817,6 @@
       'test/cursor_manager_test_api.h',
       'test/display_manager_test_api.cc',
       'test/display_manager_test_api.h',
-      'test/material_design_controller_test_api.cc',
-      'test/material_design_controller_test_api.h',
       'test/mirror_window_test_api.cc',
       'test/mirror_window_test_api.h',
       'test/overflow_bubble_view_test_api.cc',
@@ -917,6 +920,7 @@
       'common/display/display_info_unittest.cc',
       'common/material_design/material_design_controller_unittest.cc',
       'common/popup_message_unittest.cc',
+      'common/shelf/shelf_background_animator_unittest.cc',
       'common/shelf/shelf_button_pressed_metric_tracker_unittest.cc',
       'common/shelf/shelf_locking_manager_unittest.cc',
       'common/shelf/shelf_model_unittest.cc',