Provision to start base::SimpleTestTickClock at initial ticks

components/scheduler/renderer/task_cost_estimator_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 "base/test/simple_test_tick_clock.h"
 #include "components/scheduler/base/test_time_source.h"
 #include "components/scheduler/renderer/task_cost_estimator.h"
 
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace scheduler {
 
 class TaskCostEstimatorTest : public testing::Test {
  public:
-  TaskCostEstimatorTest() {}
+  TaskCostEstimatorTest() : clock_(base::TimeTicks()) {}
   ~TaskCostEstimatorTest() override {}
 
   void SetUp() override {
     test_time_source_.reset(new TestTimeSource(&clock_));
   }
 
   base::SimpleTestTickClock clock_;
   scoped_ptr<TestTimeSource> test_time_source_;
 };
 
@@ skipping 42 matching lines @@
   clock_.Advance(base::TimeDelta::FromMilliseconds(500));
   estimator.DidProcessTask(task);
   clock_.Advance(base::TimeDelta::FromMilliseconds(500));
   estimator.DidProcessTask(task);
 
   EXPECT_EQ(base::TimeDelta::FromMilliseconds(1000),
             estimator.expected_task_duration());
 }
 
 }  // namespace scheduler