Introduce HistoryClient interface

components/history.gypi

Index: components/history.gypi
diff --git a/components/history.gypi b/components/history.gypi
new file mode 100644
index 0000000000000000000000000000000000000000..8b7821e917461b88a2923a1f0bf35398189c634a
--- /dev/null
+++ b/components/history.gypi
@@ -0,0 +1,22 @@
+# 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.
+
+{
+  'targets': [
+    {
+      'target_name': 'history_core_browser',
+      'type': 'none',
+      'include_dirs': [
+        '..',
+      ],
+      'dependencies': [
+        '../base/base.gyp:base',
+        'keyed_service_core',
+      ],
+      'sources': [
+        'history/core/browser/history_client.h',
+      ],
+    },
+  ],
+}