[Chromoting] Refactor the host policy watcher so that policies can easily be added.

remoting/host/policy_hack/policy_watcher.h

 // Copyright (c) 2012 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 REMOTING_HOST_POLICY_HACK_NAT_POLICY_H_
-#define REMOTING_HOST_POLICY_HACK_NAT_POLICY_H_
+#ifndef REMOTING_HOST_POLICY_HACK_POLICY_WATCHER_H_
+#define REMOTING_HOST_POLICY_HACK_POLICY_WATCHER_H_
 
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
+#include "base/values.h"
 
 namespace base {
-class DictionaryValue;
 class SingleThreadTaskRunner;
 class TimeDelta;
 class WaitableEvent;
 }  // namespace base
 
 namespace remoting {
 namespace policy_hack {
 
-// Watches for changes to the managed remote access host NAT policies.
+// Watches for changes to the managed remote access host policies.
 // If StartWatching() has been called, then before this object can be deleted,
 // StopWatching() have completed (the provided |done| event must be signaled).
-class NatPolicy {
+class PolicyWatcher {
  public:
-  // Called with the current status of whether or not NAT traversal is enabled.
-  typedef base::Callback<void(bool)> NatEnabledCallback;
+  // Called first with all policies, and subsequently with any changed policies.
+  typedef base::Callback<void(scoped_ptr<base::DictionaryValue>)>
+      PolicyCallback;
 
-  explicit NatPolicy(scoped_refptr<base::SingleThreadTaskRunner> task_runner);
-  virtual ~NatPolicy();
+  explicit PolicyWatcher(
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+  virtual ~PolicyWatcher();
 
-  // This guarantees that the |nat_enabled_cb| is called at least once with
-  // the current policy.  After that, |nat_enabled_cb| will be called whenever
-  // a change to the nat policy is detected.
-  virtual void StartWatching(const NatEnabledCallback& nat_enabled_cb);
+  // This guarantees that the |policy_callback| is called at least once with
+  // the current policies.  After that, |policy_callback| will be called
+  // whenever a change to any policy is detected. It will then be called only
+  // with the changed policies.
+  virtual void StartWatching(const PolicyCallback& policy_callback);
 
   // Should be called after StartWatching() before the object is deleted. Calls
   // just wait for |done| to be signaled before deleting the object.
   virtual void StopWatching(base::WaitableEvent* done);
 
   // Implemented by each platform.  This message loop should be an IO message
   // loop.
-  static NatPolicy* Create(
+  static PolicyWatcher* Create(
       scoped_refptr<base::SingleThreadTaskRunner> task_runner);
 
+  // The name of the NAT traversal policy.
+  static const char kNatPolicyName[];
+
  protected:
   virtual void StartWatchingInternal() = 0;
   virtual void StopWatchingInternal() = 0;
   virtual void Reload() = 0;
 
   // Used to check if the class is on the right thread.
-  bool OnPolicyThread() const;
+  bool OnPolicyWatcherThread() const;
 
   // Takes the policy dictionary from the OS specific store and extracts the
-  // NAT traversal setting.
-  void UpdateNatPolicy(base::DictionaryValue* new_policy);
+  // relevant policies.
+  void UpdatePolicies(const base::DictionaryValue* new_policy);
 
   // Used for time-based reloads in case something goes wrong with the
   // notification system.
   void ScheduleFallbackReloadTask();
   void ScheduleReloadTask(const base::TimeDelta& delay);
 
-  static const char kNatPolicyName[];
+  // The names of policies with boolean values.
+  static const char* const kBooleanPolicyNames[];
+  static const int kBooleanPolicyNamesNum;
 
  private:
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
-  NatEnabledCallback nat_enabled_cb_;
-  bool current_nat_enabled_state_;
-  bool first_state_published_;
+  PolicyCallback policy_callback_;
+
+  scoped_ptr<base::DictionaryValue> old_policies_;
 
   // Allows us to cancel any inflight FileWatcher events or scheduled reloads.
-  base::WeakPtrFactory<NatPolicy> weak_factory_;
+  base::WeakPtrFactory<PolicyWatcher> weak_factory_;
 };
 
 }  // namespace policy_hack
 }  // namespace remoting
 
-#endif  // REMOTING_HOST_POLICY_HACK_NAT_POLICY_H_
+#endif  // REMOTING_HOST_POLICY_HACK_POLICY_WATCHER_H_