mash: Move StatusTray and StatusAreaWidget to //ash/common

This will make it possible to create a StatusAreaWidget under mojo::ash.

* Convert SystemTrayTest to use wm common types
* Remove unnecessary DEPS files

No functional changes.

BUG=619636
TEST=ash_unittests
[email protected]

Review-Url: https://codereview.chromium.org/2148593004
Cr-Commit-Position: refs/heads/master@{#405376}
diff --git a/ash/root_window_controller.cc b/ash/root_window_controller.cc
index 38c33459..fb60b34 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -19,6 +19,7 @@
 #include "ash/common/shelf/shelf_types.h"
 #include "ash/common/shell_delegate.h"
 #include "ash/common/shell_window_ids.h"
+#include "ash/common/system/status_area_widget.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/wm/always_on_top_controller.h"
 #include "ash/common/wm/container_finder.h"
@@ -43,7 +44,6 @@
 #include "ash/shelf/shelf_widget.h"
 #include "ash/shell.h"
 #include "ash/shell_factory.h"
-#include "ash/system/status_area_widget.h"
 #include "ash/touch/touch_hud_debug.h"
 #include "ash/touch/touch_hud_projection.h"
 #include "ash/touch/touch_observer_hud.h"