Provision to start base::SimpleTestTickClock at initial ticks

ash/test/task_switch_time_tracker_test_api.cc

 // Copyright 2015 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.
 
 #include "ash/test/task_switch_time_tracker_test_api.h"
 
 #include "ash/metrics/task_switch_time_tracker.h"
 #include "base/test/simple_test_tick_clock.h"
 
 namespace ash {
 namespace test {
 
 TaskSwitchTimeTrackerTestAPI::TaskSwitchTimeTrackerTestAPI(
     const std::string& histogram_name) {
-  tick_clock_ = new base::SimpleTestTickClock();
+  tick_clock_ = new base::SimpleTestTickClock(base::TimeTicks());
   time_tracker_.reset(new TaskSwitchTimeTracker(
       histogram_name, scoped_ptr<base::TickClock>(tick_clock_)));
 }
 
 TaskSwitchTimeTrackerTestAPI::~TaskSwitchTimeTrackerTestAPI() {
   tick_clock_ = nullptr;
 }
 
 void TaskSwitchTimeTrackerTestAPI::Advance(base::TimeDelta time_delta) {
   tick_clock_->Advance(time_delta);
 }
 
 bool TaskSwitchTimeTrackerTestAPI::HasLastActionTime() const {
   return time_tracker_->HasLastActionTime();
 }
 
 }  // namespace test
 }  // namespace ash