Cleanup HistoryService and HistoryBackend interface

chrome/browser/history/history_unittest.cc

 // Copyright (c) 2012 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.
 
 // History unit tests come in two flavors:
 //
 // 1. The more complicated style is that the unit test creates a full history
 //    service. This spawns a background thread for the history backend, and
 //    all communication is asynchronous. This is useful for testing more
 //    complicated things or end-to-end behavior.
@@ skipping 118 matching lines @@
   }
 
   ~HistoryBackendDBTest() override {}
 
  protected:
   friend class BackendDelegate;
 
   // Creates the HistoryBackend and HistoryDatabase on the current thread,
   // assigning the values to backend_ and db_.
   void CreateBackendAndDatabase() {
-    backend_ =
-        new HistoryBackend(history_dir_, new BackendDelegate(this), NULL);
+    backend_ = new HistoryBackend(new BackendDelegate(this), nullptr);
     backend_->Init(std::string(), false,
                    HistoryDatabaseParamsForPath(history_dir_));
     db_ = backend_->db_.get();
     DCHECK(in_mem_backend_) << "Mem backend should have been set by "
         "HistoryBackend::Init";
   }
 
   void CreateDBVersion(int version) {
     base::FilePath data_path;
     ASSERT_TRUE(PathService::Get(chrome::DIR_TEST_DATA, &data_path));
@@ skipping 1715 matching lines @@
   std::vector<PageUsageData*> results;
   db_->QuerySegmentUsage(segment_time, 10, &results);
   ASSERT_EQ(1u, results.size());
   EXPECT_EQ(url, results[0]->GetURL());
   EXPECT_EQ(segment_id, results[0]->GetID());
   EXPECT_EQ(title, results[0]->GetTitle());
   STLDeleteElements(&results);
 }
 
 }  // namespace history