Use ScopedTaskEnvironment instead of MessageLoopForUI in components tests.

components/precache/core/precache_database_unittest.cc

 // Copyright 2013 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 "components/precache/core/precache_database.h"
 
 #include <stdint.h>
 
 #include <map>
 #include <memory>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/containers/hash_tables.h"
 #include "base/files/file_path.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram_base.h"
 #include "base/test/histogram_tester.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/time/time.h"
 #include "components/history/core/browser/history_constants.h"
 #include "net/http/http_response_headers.h"
 #include "net/http/http_response_info.h"
 #include "net/http/http_util.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
 namespace {
@@ skipping 52 matching lines @@
       << "Error parsing the test headers: " << header;
   return result;
 }
 
 }  // namespace
 
 namespace precache {
 
 class PrecacheDatabaseTest : public testing::Test {
  public:
-  PrecacheDatabaseTest() {}
+  PrecacheDatabaseTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI) {}
   ~PrecacheDatabaseTest() override {}
 
  protected:
   void SetUp() override {
     precache_database_.reset(new PrecacheDatabase());
 
     ASSERT_TRUE(scoped_temp_dir_.CreateUniqueTempDir());
     base::FilePath db_path = scoped_temp_dir_.GetPath().Append(
         base::FilePath(FILE_PATH_LITERAL("precache_database")));
     ASSERT_TRUE(precache_database_->Init(db_path));
@@ skipping 37 matching lines @@
   void RecordFetchFromCache(const GURL& url,
                             const base::Time& fetch_time,
                             int64_t size);
   void RecordFetchFromCacheCellular(const GURL& url,
                                     const base::Time& fetch_time,
                                     int64_t size);
 
   // Must be declared first so that it is destroyed last.
   base::ScopedTempDir scoped_temp_dir_;
 
-  // Having this MessageLoop member variable causes base::MessageLoop::current()
-  // to be set properly.
-  base::MessageLoopForUI loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 
   std::unique_ptr<PrecacheDatabase> precache_database_;
   base::HistogramTester histograms_;
   base::HistogramTester::CountsMap expected_histogram_counts_;
 
   void ExpectNewSample(const std::string& histogram_name,
                        base::HistogramBase::Sample sample) {
     histograms_.ExpectUniqueSample(histogram_name, sample, 1);
     expected_histogram_counts_[histogram_name]++;
   }
@@ skipping 512 matching lines @@
   EXPECT_NE(PrecacheReferrerHostEntry::kInvalidId, referrer_id);
   precache_database_->GetURLListForReferrerHost(referrer_id, &_,
                                                 &actual_downloaded_urls);
   EXPECT_THAT(actual_downloaded_urls,
               ElementsAre(GURL(already_reported_but_refetch)));
 }
 
 }  // namespace
 
 }  // namespace precache