Cashew: implement backend usage API

src/policy.cc

Index: src/policy.cc
diff --git a/src/policy.cc b/src/policy.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1f5b9f60f72870010ad9fef0ac208193223935e0
--- /dev/null
+++ b/src/policy.cc
@@ -0,0 +1,16 @@
+// Copyright (c) 2010 The Chromium OS 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 "src/policy.h"
+
+#include "src/default_policy.h"
+
+namespace cashew {
+
+Policy* Policy::GetPolicy(const std::string& carrier) {
+  // for now, everyone gets the default policy
+  return new(std::nothrow) DefaultPolicy(carrier);
+}
+
+}  // namespace cashew