add the ability to yield to the event loop from the first level interpreter

threads.js

@@ -9,9 +9,6 @@ var Threads = function() {
     var mainThread = new Thread("main");
     this.add(mainThread);
     this.current = mainThread;
-    window.addEventListener("message", function () {
-        this.resume();
-    }, false);
 }
 
 Threads.prototype.add = function(thread) {

vm.js

@@ -34,6 +34,8 @@ VM.invoke = function(methodInfo, args, callback) {
 }
 
 VM.resume = function(frame, callback) {
+    var cycles = 0;
+
     var cp = frame.cp;
     var stack = frame.stack;
 
@@ -995,5 +997,13 @@ VM.resume = function(frame, callback) {
             var opName = OPCODES[op];
             throw new Error("Opcode " + opName + " [" + op + "] not supported.");
         }
+        if (VM.level <= 1) {
+            if (cycles++ > 1000) {
+                window.setZeroTimeout(function () {
+                    VM.resume(frame, callback);
+                });
+                return;
+            }
+        }
     };
 }