Forcibly clear worker ref counts on shutdown.

chrome/browser/chromeos/login/quick_unlock/pin_storage_unittest.cc

 // Copyright 2016 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/chromeos/login/quick_unlock/pin_storage.h"
 #include "chrome/browser/chromeos/login/quick_unlock/pin_storage_factory.h"
 #include "chrome/browser/chromeos/login/quick_unlock/quick_unlock_utils.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/test/base/testing_profile.h"
 #include "components/prefs/pref_service.h"
+#include "content/public/test/test_browser_thread_bundle.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
 
 class PinStorageUnitTest : public testing::Test {
  protected:
   PinStorageUnitTest() : profile_(new TestingProfile()) {}
   ~PinStorageUnitTest() override {}
 
   // testing::Test:
   void SetUp() override { chromeos::EnableQuickUnlockForTesting(); }
 
   std::unique_ptr<TestingProfile> profile_;
+  content::TestBrowserThreadBundle thread_bundle_;
 
   DISALLOW_COPY_AND_ASSIGN(PinStorageUnitTest);
 };
 
 }  // namespace
 
 // Provides test-only PinStorage APIs.
 class PinStorageTestApi {
  public:
   // Does *not* take ownership over |pin_storage|.
@@ skipping 122 matching lines @@
   pin_storage->SetPin("1111");
   pin_storage->MarkStrongAuth();
   EXPECT_TRUE(pin_storage->IsPinAuthenticationAvailable());
 
   // Remove all of the strong auth time so that we have a strong auth timeout.
   pin_storage_test.ReduceRemainingStrongAuthTimeBy(
       chromeos::PinStorage::kStrongAuthTimeout + base::TimeDelta::FromHours(1));
 
   EXPECT_FALSE(pin_storage->IsPinAuthenticationAvailable());
 }