Bug 612311: Add some instrumentation. r=me

dom/workers/test/suspend_worker.js

@@ -5,6 +5,7 @@
 var counter = 0;
 
 var interval = setInterval(function() {
+  dump("WorkerAlive\n"); 
   postMessage(++counter);
 }, 100);
 

dom/workers/test/terminate_worker.js

@@ -10,4 +10,4 @@ onmessage = function(event) {
   throw "No messages should reach me!";
 }
 
-setInterval(function() { postMessage("Still alive!"); }, 100);
+setInterval(function() { dump("WorkerAlive\n"); postMessage("Still alive!"); }, 100);