Re-factor network_event_log

chromeos/network/managed_state.h

Index: chromeos/network/managed_state.h
diff --git a/chromeos/network/managed_state.h b/chromeos/network/managed_state.h
index c7964a3b6d09d36a9568e580451d6d1d2dc457c1..4196d34729e7265f20e598a646fb8dc4c6331e14 100644
--- a/chromeos/network/managed_state.h
+++ b/chromeos/network/managed_state.h
@@ -41,7 +41,8 @@ class ManagedState {
   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;
 
@@ -64,7 +65,8 @@ class ManagedState {
   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);