ash:Shelf - Added UMA stats for ShelfAlignment

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 62379acd06aebdf01ca5cf0c590760ce59ca0171..7dfc6213b180c5b317d824a50d8d73d44fa6e4ce 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "ash/ash_export.h"
+#include "ash/periodic_metrics_recorder.h"
 #include "ash/shelf/shelf_types.h"
 #include "ash/system/user/login_status.h"
 #include "ash/wm/system_modal_container_event_filter_delegate.h"
@@ -575,6 +576,7 @@ class ASH_EXPORT Shell
 
   std::vector<WindowAndBoundsPair> to_restore_;
 
+  scoped_ptr<AshPeriodicMetricsRecorder> periodic_metrics_recorder_;
   scoped_ptr<keyboard::KeyboardController> keyboard_controller_;
   scoped_ptr<NestedDispatcherController> nested_dispatcher_controller_;
   scoped_ptr<AcceleratorController> accelerator_controller_;