Track active references in ShillClientHelper (Take 2)

chromeos/dbus/shill_client_helper.h

Index: chromeos/dbus/shill_client_helper.h
diff --git a/chromeos/dbus/shill_client_helper.h b/chromeos/dbus/shill_client_helper.h
index 12cd9948cf2f04b2bc86ae3e8293d53bd59a1ef6..a52fc222eae758b43c86d32bd1b97554f9f044db 100644
--- a/chromeos/dbus/shill_client_helper.h
+++ b/chromeos/dbus/shill_client_helper.h
@@ -41,6 +41,8 @@ namespace chromeos {
 // A class to help implement Shill clients.
 class ShillClientHelper {
  public:
+  class RefHolder;
+
   // A callback to handle PropertyChanged signals.
   typedef base::Callback<void(const std::string& name,
                               const base::Value& value)> PropertyChangedHandler;
@@ -68,11 +70,17 @@ class ShillClientHelper {
   // A callback that handles responses for methods with boolean results.
   typedef base::Callback<void(bool result)> BooleanCallback;
 
+  // Callback used to notify owner when this can be safely released.
+  typedef base::Callback<void(ShillClientHelper* helper)> ReleasedCallback;
 
-  ShillClientHelper(dbus::Bus* bus, dbus::ObjectProxy* proxy);
+  explicit ShillClientHelper(dbus::ObjectProxy* proxy);
 
   virtual ~ShillClientHelper();
 
+  // Sets |released_callback_|. This is optional and should only be called at
+  // most once.
+  void SetReleasedCallback(ReleasedCallback callback);
+
   // Adds an |observer| of the PropertyChanged signal.
   void AddPropertyChangedObserver(ShillPropertyChangedObserver* observer);
 
@@ -131,6 +139,8 @@ class ShillClientHelper {
       const ListValueCallback& callback,
       const ErrorCallback& error_callback);
 
+  const dbus::ObjectProxy* object_proxy() const { return proxy_; }
+
   // Appends the value (basic types and string-to-string dictionary) to the
   // writer as a variant.
   static void AppendValueDataAsVariant(dbus::MessageWriter* writer,
@@ -141,6 +151,13 @@ class ShillClientHelper {
       dbus::MessageWriter* writer,
       const base::DictionaryValue& dictionary);
 
+ protected:
+  // Reference / Ownership management. If the number of active refs (observers
+  // + in-progress method calls) becomes 0, |released_callback_| (if set) will
+  // be called.
+  void AddRef();
+  void Release();
+
  private:
   // Starts monitoring PropertyChanged signal.
   void MonitorPropertyChangedInternal(const std::string& interface_name);
@@ -154,6 +171,8 @@ class ShillClientHelper {
   void OnPropertyChanged(dbus::Signal* signal);
 
   dbus::ObjectProxy* proxy_;
+  ReleasedCallback released_callback_;
+  int active_refs_;
   PropertyChangedHandler property_changed_handler_;
   ObserverList<ShillPropertyChangedObserver, true /* check_empty */>
       observer_list_;