WIP: Eliminate event.target() usage from TrayEventFilter

ash/system/tray/tray_bubble_wrapper.cc

Index: ash/system/tray/tray_bubble_wrapper.cc
diff --git a/ash/system/tray/tray_bubble_wrapper.cc b/ash/system/tray/tray_bubble_wrapper.cc
index f904cb210f8833389ded28da5104cb0e643266af..2294e11012e59352d80f59798c6b26bf0f53058d 100644
--- a/ash/system/tray/tray_bubble_wrapper.cc
+++ b/ash/system/tray/tray_bubble_wrapper.cc
@@ -13,6 +13,8 @@
 #include "ui/views/bubble/tray_bubble_view.h"
 #include "ui/views/widget/widget.h"
 
+#include "base/debug/stack_trace.h"
+
 namespace ash {
 
 TrayBubbleWrapper::TrayBubbleWrapper(TrayBackgroundView* tray,
@@ -22,6 +24,8 @@ TrayBubbleWrapper::TrayBubbleWrapper(TrayBackgroundView* tray,
   bubble_widget_ = views::BubbleDialogDelegateView::CreateBubble(bubble_view_);
   bubble_widget_->AddObserver(this);
 
+//  base::debug::StackTrace().Print();
+
   TrayBackgroundView::InitializeBubbleAnimations(bubble_widget_);
   tray_->UpdateBubbleViewArrow(bubble_view_);
   bubble_view_->InitializeAndShowBubble();