WIP: Eliminate event.target() usage from TrayEventFilter

ash/shelf/overflow_bubble.cc

Index: ash/shelf/overflow_bubble.cc
diff --git a/ash/shelf/overflow_bubble.cc b/ash/shelf/overflow_bubble.cc
index c87f77a083bd219a6ceb8c28fc286def91991379..0dd26dc00166f4d185c777113298a671d01b51d7 100644
--- a/ash/shelf/overflow_bubble.cc
+++ b/ash/shelf/overflow_bubble.cc
@@ -72,12 +72,14 @@ void OverflowBubble::ProcessPressedEvent(
 }
 
 void OverflowBubble::OnMousePressed(const ui::MouseEvent& event,
-                                    const gfx::Point& location_in_screen) {
+                                    const gfx::Point& location_in_screen,
+                                    views::Widget* target) {
   ProcessPressedEvent(location_in_screen);
 }
 
 void OverflowBubble::OnTouchPressed(const ui::TouchEvent& event,
-                                    const gfx::Point& location_in_screen) {
+                                    const gfx::Point& location_in_screen,
+                                    views::Widget* target) {
   ProcessPressedEvent(location_in_screen);
 }