Change ui::Event::time_stamp from TimeDelta to TimeTicks

ash/keyboard_uma_event_filter.h

Index: ash/keyboard_uma_event_filter.h
diff --git a/ash/keyboard_uma_event_filter.h b/ash/keyboard_uma_event_filter.h
index a52cf357180e2acad782fa3fa5bcb7c834ef7cc1..97dbe2bf784496cd6cb7eaef11ba39f8aed0b9db 100644
--- a/ash/keyboard_uma_event_filter.h
+++ b/ash/keyboard_uma_event_filter.h
@@ -25,7 +25,7 @@ class KeyboardUMAEventFilter : public ui::EventHandler {
 
  private:
   // The timestamp of the last character keystroke.
-  base::TimeDelta last_keystroke_time_;
+  base::TimeTicks last_keystroke_time_;
 
   DISALLOW_COPY_AND_ASSIGN(KeyboardUMAEventFilter);
 };