Provision to start base::SimpleTestTickClock at initial ticks

chrome/browser/memory/tab_manager_web_contents_data_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 "chrome/browser/memory/tab_manager_web_contents_data.h"
 
 #include "base/test/histogram_tester.h"
 #include "base/test/simple_test_tick_clock.h"
 #include "chrome/test/base/chrome_render_view_host_test_harness.h"
 #include "chrome/test/base/testing_profile.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/test/web_contents_tester.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::WebContents;
 using content::WebContentsTester;
 
 namespace memory {
 namespace {
 
 class TabManagerWebContentsDataTest : public ChromeRenderViewHostTestHarness {
  public:
-  TabManagerWebContentsDataTest() : ChromeRenderViewHostTestHarness() {}
+  TabManagerWebContentsDataTest()
+      : ChromeRenderViewHostTestHarness(), test_clock_(base::TimeTicks()) {}
 
   void SetUp() override {
     ChromeRenderViewHostTestHarness::SetUp();
     tab_data_ = CreateWebContentsAndTabData(&web_contents_);
     tab_data_->set_test_tick_clock(&test_clock_);
   }
 
   void TearDown() override {
     tab_data_->set_test_tick_clock(nullptr);
     web_contents_.reset();
@@ skipping 164 matching lines @@
   test_clock().Advance(base::TimeDelta::FromSeconds(7));
   tab_data()->SetDiscardState(false);
 
   EXPECT_EQ(1,
             histograms.GetTotalCountsForPrefix(kHistogramName).begin()->second);
 
   histograms.ExpectBucketCount(kHistogramName, 12000, 1);
 }
 
 }  // namespace memory