Cashew: implement backend usage API

src/policy.h

Index: src/policy.h
diff --git a/src/policy.h b/src/policy.h
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+// 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.
+
+#ifndef SRC_POLICY_H_
+#define SRC_POLICY_H_
+
+#include <glib.h>
+
+#include <string>
+
+#include "src/data_plan.h"
+
+namespace cashew {
+
+// interface for carrier policy
+class Policy {
+  public:
+    virtual ~Policy() {}
+
+    // what carrier is associated with this policy?
+    virtual const std::string& GetCarrier() const = 0;
+
+    // how often should a service request updates via the carrier usage API?
+    // return value is in seconds
+    virtual guint GetUpdateTimerIdleSecs(const DataPlanList& plans) const = 0;
+
+    // should we emit a data plans update for the change from |old_plans|
+    // to |new_plans|?
+    // NOTE: user might also want to influence this from the Chrome side
+    virtual bool ShouldEmitDataPlansUpdate(const DataPlanList& old_plans,
+        const DataPlanList& new_plans) const = 0;
+
+    // factory
+    // return appropriate concrete impl for |carrier|
+    // caller owns returned Policy and is responsible for deleting it
+    static Policy* GetPolicy(const std::string& carrier);
+};
+
+}  // namespace cashew
+
+#endif  // SRC_POLICY_H_