Re-factor network_event_log

chromeos/network/managed_state.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 CHROMEOS_NETWORK_MANAGED_STATE_H_
 #define CHROMEOS_NETWORK_MANAGED_STATE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 23 matching lines @@
   // This will construct and return a new instance of the approprate class
   // based on |type|.
   static ManagedState* Create(ManagedType type, const std::string& path);
 
   // Returns the specific class pointer if this is the correct type, or
   // NULL if it is not.
   NetworkState* AsNetworkState();
   DeviceState* AsDeviceState();
 
   // Called by NetworkStateHandler when a property changes. Returns true if
-  // the property was recognized and parsed successfully.
+  // the property was recognized, parsed successfully, and different from
+  // the previous value.
   virtual bool PropertyChanged(const std::string& key,
                                const base::Value& value) = 0;
 
   // Called by NetworkStateHandler after all calls to PropertyChanged for the
   // initial set of properties. Used to update state requiring multiple
   // parsed properties, e.g. name from hex_ssid in NetworkState.
   virtual void InitialPropertiesReceived();
 
   const ManagedType managed_type() const { return managed_type_; }
   const std::string& path() const { return path_; }
   const std::string& name() const { return name_; }
   const std::string& type() const { return type_; }
   bool is_observed() const { return is_observed_; }
   void set_is_observed(bool is_observed) { is_observed_ = is_observed; }
 
  protected:
   ManagedState(ManagedType type, const std::string& path);
 
   // Parses common property keys (name, type).
   bool ManagedStatePropertyChanged(const std::string& key,
                                    const base::Value& value);
 
-  // Helper methods that log warnings and return false if parsing failed.
+  // Helper methods that log warnings and return true if parsing succeeded and
+  // the new value does not match the existing output value.
   bool GetBooleanValue(const std::string& key,
                        const base::Value& value,
                        bool* out_value);
   bool GetIntegerValue(const std::string& key,
                        const base::Value& value,
                        int* out_value);
   bool GetStringValue(const std::string& key,
                       const base::Value& value,
                       std::string* out_value);
 
@@ skipping 13 matching lines @@
 
   // Tracks when the state is being observed.
   bool is_observed_;
 
   DISALLOW_COPY_AND_ASSIGN(ManagedState);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_NETWORK_MANAGED_STATE_H_