Rename ash desktop_background to wallpaper.

ash/ash.gyp

Index: ash/ash.gyp
diff --git a/ash/ash.gyp b/ash/ash.gyp
index 72516c7c240ff1afbc229bd818dcd343767b8d96..c69b8e39322a485cdbea0bc56454756f3f973d02 100644
--- a/ash/ash.gyp
+++ b/ash/ash.gyp
@@ -542,13 +542,6 @@
       'debug.h',
       'default_wallpaper_delegate.cc',
       'default_wallpaper_delegate.h',
-      'desktop_background/desktop_background_controller.cc',
-      'desktop_background/desktop_background_controller.h',
-      'desktop_background/desktop_background_controller_observer.h',
-      'desktop_background/desktop_background_view.cc',
-      'desktop_background/desktop_background_view.h',
-      'desktop_background/desktop_background_widget_controller.cc',
-      'desktop_background/desktop_background_widget_controller.h',
       'display/cursor_window_controller.cc',
       'display/cursor_window_controller.h',
       'display/display_animator.h',
@@ -710,6 +703,13 @@
       'utility/screenshot_controller.h',
       'virtual_keyboard_controller.cc',
       'virtual_keyboard_controller.h',
+      'wallpaper/wallpaper_controller.cc',
+      'wallpaper/wallpaper_controller.h',
+      'wallpaper/wallpaper_controller_observer.h',
+      'wallpaper/wallpaper_view.cc',
+      'wallpaper/wallpaper_view.h',
+      'wallpaper/wallpaper_widget_controller.cc',
+      'wallpaper/wallpaper_widget_controller.h',
       'wm/ash_focus_rules.cc',
       'wm/ash_focus_rules.h',
       'wm/ash_native_cursor_manager.cc',
@@ -778,8 +778,6 @@
       'wm/stacking_controller.h',
       'wm/stylus_metrics_recorder.cc',
       'wm/stylus_metrics_recorder.h',
-      'wm/system_background_controller.cc',
-      'wm/system_background_controller.h',
       'wm/system_gesture_event_filter.cc',
       'wm/system_gesture_event_filter.h',
       'wm/system_modal_container_event_filter.cc',
@@ -787,6 +785,8 @@
       'wm/system_modal_container_event_filter_delegate.h',
       'wm/system_modal_container_layout_manager.cc',
       'wm/system_modal_container_layout_manager.h',
+      'wm/system_wallpaper_controller.cc',
+      'wm/system_wallpaper_controller.h',
       'wm/toplevel_window_event_handler.cc',
       'wm/toplevel_window_event_handler.h',
       'wm/video_detector.cc',
@@ -983,7 +983,6 @@
       'content/display/screen_orientation_controller_chromeos_unittest.cc',
       'content/keyboard_overlay/keyboard_overlay_delegate_unittest.cc',
       'content/keyboard_overlay/keyboard_overlay_view_unittest.cc',
-      'desktop_background/desktop_background_controller_unittest.cc',
       'dip_unittest.cc',
       'display/cursor_window_controller_unittest.cc',
       'display/display_change_observer_chromeos_unittest.cc',
@@ -1040,6 +1039,7 @@
       'touch/touchscreen_util_unittest.cc',
       'utility/screenshot_controller_unittest.cc',
       'virtual_keyboard_controller_unittest.cc',
+      'wallpaper/wallpaper_controller_unittest.cc',
       'wm/always_on_top_controller_unittest.cc',
       'wm/ash_focus_rules_unittest.cc',
       'wm/ash_native_cursor_manager_unittest.cc',