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

ash/keyboard_uma_event_filter.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_KEYBOARD_UMA_EVENT_FILTER_H_
 #define ASH_KEYBOARD_UMA_EVENT_FILTER_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "ui/events/event_handler.h"
 
 namespace ash {
 
 // EventFilter for tracking keyboard-related metrics, which intercepts events
 // before they are processed by the usual path and logs metrics about the
 // events.
 class KeyboardUMAEventFilter : public ui::EventHandler {
  public:
   KeyboardUMAEventFilter();
   ~KeyboardUMAEventFilter() override;
 
   // ui::EventHandler overrides:
   void OnKeyEvent(ui::KeyEvent* event) override;
 
  private:
   // The timestamp of the last character keystroke.
-  base::TimeDelta last_keystroke_time_;
+  base::TimeTicks last_keystroke_time_;
 
   DISALLOW_COPY_AND_ASSIGN(KeyboardUMAEventFilter);
 };
 
 }  // namespace ash
 
 #endif  // ASH_KEYBOARD_UMA_EVENT_FILTER_H_