Introduce HistoryClient interface

components/history/core/browser/test_history_client.cc

Index: components/history/core/browser/test_history_client.cc
diff --git a/components/history/core/browser/test_history_client.cc b/components/history/core/browser/test_history_client.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8bbb9b3eaf4b30efa9249614c29a0793ce402914
--- /dev/null
+++ b/components/history/core/browser/test_history_client.cc
@@ -0,0 +1,13 @@
+// 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.
+
+#include "components/history/core/browser/test_history_client.h"
+
+namespace history {
+
+TestHistoryClient::TestHistoryClient() {}
+
+TestHistoryClient::~TestHistoryClient() {}
+
+}  // namespace history