Provision to start base::SimpleTestTickClock at initial ticks

ash/shelf/shelf_button_pressed_metric_tracker_unittest.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/shelf/shelf_button_pressed_metric_tracker.h"
 
 #include <utility>
 
 #include "ash/shelf/shelf.h"
 #include "ash/test/ash_test_base.h"
@@ skipping 100 matching lines @@
 void ShelfButtonPressedMetricTrackerTest::SetUp() {
   AshTestBase::SetUp();
 
   Shelf* shelf = Shelf::ForPrimaryDisplay();
   ShelfViewTestAPI shelf_view_test_api(ShelfTestAPI(shelf).shelf_view());
 
   metric_tracker_ = shelf_view_test_api.shelf_button_pressed_metric_tracker();
 
   ShelfButtonPressedMetricTrackerTestAPI test_api(metric_tracker_);
 
-  scoped_ptr<base::TickClock> test_tick_clock(new base::SimpleTestTickClock());
+  // Ensure the TickClock->NowTicks() doesn't return base::TimeTicks because
+  // ShelfButtonPressedMetricTracker interprets that value as unset.
+  scoped_ptr<base::TickClock> test_tick_clock(new base::SimpleTestTickClock(
+      base::TimeTicks() + base::TimeDelta::FromMilliseconds(100)));
   tick_clock_ = static_cast<base::SimpleTestTickClock*>(test_tick_clock.get());
   test_api.SetTickClock(std::move(test_tick_clock));
-
-  // Ensure the TickClock->NowTicks() doesn't return base::TimeTicks because
-  // ShelfButtonPressedMetricTracker interprets that value as unset.
-  tick_clock_->Advance(base::TimeDelta::FromMilliseconds(100));
 }
 
 void ShelfButtonPressedMetricTrackerTest::TearDown() {
   tick_clock_ = nullptr;
 
   AshTestBase::TearDown();
 }
 
 void ShelfButtonPressedMetricTrackerTest::ButtonPressed(
     const ui::Event& event) {
@@ skipping 154 matching lines @@
 
   histogram_tester.ExpectTotalCount(
       kTimeBetweenWindowMinimizedAndActivatedActionsHistogramName, 1);
   histogram_tester.ExpectBucketCount(
       kTimeBetweenWindowMinimizedAndActivatedActionsHistogramName,
       kTimeDeltaInMilliseconds, 1);
 }
 
 }  // namespace test
 }  // namespace ash