Implement the W3C "status" endpoint in the firefoxdriver XPI

They say that there's nothing worse than someone trying to be
something that they're not. We ignore this advice and will
therefore serve this old mutton as fresh lamb.

Author: shs96c

javascript/firefox-driver/js/nsCommandProcessor.js

@@ -669,7 +669,25 @@ nsCommandProcessor.prototype.getStatus = function(response) {
   var xulRuntime = Components.classes['@mozilla.org/xre/app-info;1'].
       getService(Components.interfaces.nsIXULRuntime);
 
+  var sessionStore = Components.
+      classes['@googlecode.com/webdriver/wdsessionstoreservice;1'].
+      getService(Components.interfaces.nsISupports).
+      wrappedJSObject;
+
+  var allSessions = sessionStore.getSessions();
+  var readyState = false;
+  var message = '';
+  if (goog.array.isEmpty(allSessions)) {
+    readyState = true;
+    message = 'No currently active sessions';
+  } else {
+    readyState = false;
+    message = 'Currently active sessions: ' + allSessions;
+  }
+
   response.value = {
+    'ready': readyState,
+    'message': message,
     'os': {
       'arch': (function() {
         try {

javascript/firefox-driver/js/sessionstore.js

@@ -255,11 +255,20 @@ wdSessionStoreService.prototype.getSession = function(sessionId) {
     var session = this.sessions_[sessionId].wrappedJSObject;  // XPConnect
     return this.sessions_[sessionId];
   }
+  throw Components.results.NS_ERROR_NOT_AVAILABLE;
+};
+
+
+/**
+ * Retrieve all the current active session IDs.
+ * @returns {!Array.<string>}
+ */
+wdSessionStoreService.prototype.getSessions = function() {
   var sessions = [];
-  for (var session in this.sessions_) {
-    sessions.push(session);
+  for (var sessionId in this.sessions_) {
+    sessions.push(sessionId);
   }
-  throw Components.results.NS_ERROR_NOT_AVAILABLE;
+  return sessions;
 };