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

ash/shelf/shelf_button_pressed_metric_tracker_unittest.cc

Index: ash/shelf/shelf_button_pressed_metric_tracker_unittest.cc
diff --git a/ash/shelf/shelf_button_pressed_metric_tracker_unittest.cc b/ash/shelf/shelf_button_pressed_metric_tracker_unittest.cc
index 8ddb0bf843926cd856a72581e7205b69b9085580..4052f9698e70616765c622f5e13d2d1791159bd4 100644
--- a/ash/shelf/shelf_button_pressed_metric_tracker_unittest.cc
+++ b/ash/shelf/shelf_button_pressed_metric_tracker_unittest.cc
@@ -52,9 +52,8 @@ class DummyEvent : public ui::Event {
 int DummyEvent::next_unique_id_ = 0;
 
 DummyEvent::DummyEvent()
-    : Event(ui::ET_GESTURE_TAP, base::TimeDelta(), 0),
-      unique_id_(next_unique_id_++) {
-}
+    : Event(ui::ET_GESTURE_TAP, base::TimeTicks(), 0),
+      unique_id_(next_unique_id_++) {}
 
 DummyEvent::~DummyEvent() {
 }
@@ -162,7 +161,7 @@ void ShelfButtonPressedMetricTrackerTest::ButtonPressed(
 TEST_F(ShelfButtonPressedMetricTrackerTest,
        Launcher_ButtonPressed_MouseIsRecordedWhenIconActivatedByMouse) {
   const ui::MouseEvent mouse_event(ui::ET_MOUSE_PRESSED, gfx::Point(),
-                                   gfx::Point(), base::TimeDelta(), 0, 0);
+                                   gfx::Point(), base::TimeTicks(), 0, 0);
 
   base::UserActionTester user_action_tester;
   ButtonPressed(mouse_event);
@@ -175,7 +174,7 @@ TEST_F(ShelfButtonPressedMetricTrackerTest,
 TEST_F(ShelfButtonPressedMetricTrackerTest,
        Launcher_ButtonPressed_MouseIsRecordedWhenIconActivatedByTouch) {
   const ui::TouchEvent touch_event(ui::ET_GESTURE_TAP, gfx::Point(), 0,
-                                   base::TimeDelta());
+                                   base::TimeTicks());
 
   base::UserActionTester user_action_tester;
   ButtonPressed(touch_event);