Introduce HistoryClient interface

chrome/browser/history/chrome_history_client.h

+// Copyright 2014 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.
+
+#ifndef CHROME_BROWSER_HISTORY_CHROME_HISTORY_CLIENT_H_
+#define CHROME_BROWSER_HISTORY_CHROME_HISTORY_CLIENT_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "components/history/core/browser/history_client.h"
+#include "components/keyed_service/core/keyed_service.h"
+
+class Profile;
+class HistoryService;
+
+namespace history {
+
+class ChromeHistoryClient : public HistoryClient,

[blundell, 2014/05/27 09:56:38]

should have a class comment.

[sdefresne, 2014/05/28 17:10:42]

Done.

+                            public KeyedService {
+ public:
+  explicit ChromeHistoryClient(Profile* profile);
+
+  HistoryService* history_service() const {

[blundell, 2014/05/27 09:56:38]

const methods should return const pointers (or it shouldn't be a const method,
one of the two).

[sdefresne, 2014/05/28 17:10:42]

Done.

+    return history_service_.get();
+  }
+
+  // KeyedService:
+  virtual void Shutdown() OVERRIDE;
+
+ private:
+  scoped_ptr<HistoryService> history_service_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeHistoryClient);
+};
+
+}  // namespace history
+
+#endif  // CHROME_BROWSER_HISTORY_CHROME_HISTORY_CLIENT_H_