Shill: Delay the ConnectToSignal call until an observer is added.

chromeos/dbus/shill_client_helper.cc

 // 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.
 
 #include "chromeos/dbus/shill_client_helper.h"
 
 #include "base/bind.h"
 #include "base/values.h"
 #include "dbus/message.h"
 #include "dbus/object_proxy.h"
@@ skipping 17 matching lines @@
 }
 
 ShillClientHelper::~ShillClientHelper() {
   LOG_IF(ERROR, observer_list_.size() != 0u)
       << "ShillClientHelper destroyed with active observers: "
       << observer_list_.size();
 }
 
 void ShillClientHelper::AddPropertyChangedObserver(
     ShillPropertyChangedObserver* observer) {
+  // Excecute all the pending MonitorPropertyChanged calls.
+  for (size_t i = 0; i < interfaces_to_be_monitored_.size(); ++i) {
+    MonitorPropertyChangedInternal(interfaces_to_be_monitored_[i]);
+  }
+  interfaces_to_be_monitored_.clear();
+
   observer_list_.AddObserver(observer);
 }
 
 void ShillClientHelper::RemovePropertyChangedObserver(
     ShillPropertyChangedObserver* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
 void ShillClientHelper::MonitorPropertyChanged(
     const std::string& interface_name) {
+  if (observer_list_.size() > 0) {
+    // Effectively monitor the PropertyChanged now.
+    MonitorPropertyChangedInternal(interface_name);
+  } else {
+    // Delay the ConnectToSignal until an observer is added.
+    interfaces_to_be_monitored_.push_back(interface_name);
+  }
+}
+
+void ShillClientHelper::MonitorPropertyChangedInternal(
+    const std::string& interface_name) {
   // We are not using dbus::PropertySet to monitor PropertyChanged signal
   // because the interface is not "org.freedesktop.DBus.Properties".
   proxy_->ConnectToSignal(interface_name,
                           flimflam::kMonitorPropertyChanged,
                           base::Bind(&ShillClientHelper::OnPropertyChanged,
                                      weak_ptr_factory_.GetWeakPtr()),
                           base::Bind(&ShillClientHelper::OnSignalConnected,
                                      weak_ptr_factory_.GetWeakPtr()));
 }
 
@@ skipping 279 matching lines @@
   if (response) {
     // Error message may contain the error message as string.
     dbus::MessageReader reader(response);
     error_name = response->GetErrorName();
     reader.PopString(&error_message);
   }
   error_callback.Run(error_name, error_message);
 }
 
 }  // namespace chromeos