Exports gesture manager to a separate file and adds its unittests.

athena/home/home_card_constants.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 ATHENA_HOME_HOME_CARD_CONSTANTS_H_
+#define ATHENA_HOME_HOME_CARD_CONSTANTS_H_
+
+#include "athena/athena_export.h"
+
+namespace athena {
+
+// The height of the home card in BOTTOM state.
+ATHENA_EXPORT extern const int kHomeCardHeight;
+
+// The height of the home card of MINIMIZED state.
+ATHENA_EXPORT extern const int kHomeCardMinimizedHeight;
+
+}  // namespace athena
+
+#endif  // ATHENA_HOME_HOME_CARD_CONSTANTS_H_