Adds tracing to investigate infinite calls to SetAutoHideBehavior

ash/common/shelf/wm_shelf.h

Index: ash/common/shelf/wm_shelf.h
diff --git a/ash/common/shelf/wm_shelf.h b/ash/common/shelf/wm_shelf.h
index 526b9c5f6878d4cda7f38e73ff08e52d0534d32f..b2800772eb3ad2720a9119c681683e4b774df511 100644
--- a/ash/common/shelf/wm_shelf.h
+++ b/ash/common/shelf/wm_shelf.h
@@ -11,6 +11,7 @@
 #include "ash/common/shelf/shelf_layout_manager_observer.h"
 #include "ash/public/cpp/shelf_types.h"
 #include "base/observer_list.h"
+#include "base/time/time.h"
 
 namespace gfx {
 class Rect;
@@ -176,6 +177,10 @@ class ASH_EXPORT WmShelf : public ShelfLayoutManagerObserver {
 
   base::ObserverList<WmShelfObserver> observers_;
 
+  // Temporary. Used to investigate http://crbug.com/665093 .
+  base::TimeTicks time_last_auto_hide_change_;
+  int count_auto_hide_changes_ = 0;
+
   DISALLOW_COPY_AND_ASSIGN(WmShelf);
 };