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 fa54faa81839841fafda3b96742b96063468c9ea..99c95310e8195e598855099d61139a7c262e1401 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"
@@ -580,6 +581,7 @@ class ASH_EXPORT Shell
 
   std::vector<WindowAndBoundsPair> to_restore_;
 
+  scoped_ptr<PeriodicMetricsRecorder> periodic_metrics_recorder_;
   scoped_ptr<keyboard::KeyboardController> keyboard_controller_;
   scoped_ptr<NestedDispatcherController> nested_dispatcher_controller_;
   scoped_ptr<AcceleratorController> accelerator_controller_;