[ChromeDriver] Added CommandListener interface

chrome/test/chromedriver/commands.cc

Index: chrome/test/chromedriver/commands.cc
diff --git a/chrome/test/chromedriver/commands.cc b/chrome/test/chromedriver/commands.cc
index 25a7d698647c40c425a005e160caf8015956c0db..5aefd9411fdcbab325fde3241274ca4d41ff764e 100644
--- a/chrome/test/chromedriver/commands.cc
+++ b/chrome/test/chromedriver/commands.cc
@@ -151,8 +151,14 @@ void ExecuteSessionCommandOnSessionThread(
     VLOG(0) << "COMMAND " << command_name << " "
             << FormatValueForDisplay(*params);
   }
+
+  Status status = session->OnCommand(std::string(command_name));

[klm, 2014/06/16 16:11:29]

I am concerned that this is only done on session commands -- from under
ExecuteSessionCommand, but not from Execute{Window,Element,Alert}Command, unless
those go through ExecuteSessionCommand, which I don't see that they would,
although then I'm not sure how the window/element/alert commands end up running
on the session thread... See http_handler.cc for the top level command dispatch
logic.

The listener should get invoked on all commands, not just session, and then it's
up to the listener implementation to decide what to do on what commands.

[johnmoore, 2014/06/16 17:28:34]

I believe that the window and element commands do go through
ExecuteSessionCommand due to overloading of HttpHandler::WrapToCommand. I
checked to make sure OnCommand would be triggered for "Navigate" (window
command) and "FindElement" (element command). I have now confirmed the same for
"GetAlertMessage" (alert command); it is triggered as well.

+
+  if (status.IsError())
+    LOG(ERROR) << "Error when notifying listeners of command";
+
   scoped_ptr<base::Value> value;
-  Status status = command.Run(session, *params, &value);
+  status = command.Run(session, *params, &value);
 
   if (status.IsError() && session->chrome) {
     if (!session->quit && session->chrome->HasCrashedWebView()) {