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

chromeos/dbus/shill_client_helper.cc

Index: chromeos/dbus/shill_client_helper.cc
diff --git a/chromeos/dbus/shill_client_helper.cc b/chromeos/dbus/shill_client_helper.cc
index c83bfe0b9d3530f1c9f859eeba37beb225e625d7..c0c5890712cf9bda4533edcd3611ed475b25897e 100644
--- a/chromeos/dbus/shill_client_helper.cc
+++ b/chromeos/dbus/shill_client_helper.cc
@@ -35,6 +35,14 @@ ShillClientHelper::~ShillClientHelper() {
 
 void ShillClientHelper::AddPropertyChangedObserver(
     ShillPropertyChangedObserver* observer) {
+  // Excecutes all the pending MonitorPropertyChanged calls.

[hashimoto, 2013/02/13 05:56:00]

nitty-nit: s/Executes/Execute/
Our style guide does not require "-s" for implementation comments.
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Implementation...

[deymo, 2013/02/13 19:18:11]

Done.

+  for (std::vector<std::string>::iterator it =

[hashimoto, 2013/02/13 05:56:00]

nit: "for (size_t i = 0; i < interfaces_to_be_monitored_.end(); ++i)" is more
common style in our code base to iterate over a vector.

[deymo, 2013/02/13 19:18:11]

Done.

+      interfaces_to_be_monitored_.begin();
+      it != interfaces_to_be_monitored_.end(); ++it) {
+    MonitorPropertyChangedInternal(*it);
+  }
+  interfaces_to_be_monitored_.clear();
+
   observer_list_.AddObserver(observer);
 }
 
@@ -45,6 +53,17 @@ void ShillClientHelper::RemovePropertyChangedObserver(
 
 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,