Introduce HistoryClient interface

components/history/core/browser/test_history_client.h

Index: components/history/core/browser/test_history_client.h
diff --git a/components/history/core/browser/test_history_client.h b/components/history/core/browser/test_history_client.h
new file mode 100644
index 0000000000000000000000000000000000000000..4ceb02607f8a81d753928ac06dbd07f9b2df70e4
--- /dev/null
+++ b/components/history/core/browser/test_history_client.h
@@ -0,0 +1,23 @@
+// 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 COMPONENTS_HISTORY_CORE_BROWSER_TEST_HISTORY_CLIENT_H_
+#define COMPONENTS_HISTORY_CORE_BROWSER_TEST_HISTORY_CLIENT_H_
+
+#include "components/history/core/browser/history_client.h"
+
+namespace history {
+
+class TestHistoryClient : public HistoryClient {
+ public:
+  TestHistoryClient();
+  virtual ~TestHistoryClient();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TestHistoryClient);
+};
+
+}  // namespace history
+
+#endif  // COMPONENTS_HISTORY_CORE_BROWSER_TEST_HISTORY_CLIENT_H_