Updated the screen implementation according to the spec

web/esop-ext.js

@@ -79,6 +79,8 @@ function ESOPExtensions() {
     // also, we need to set up the screen vector
     var rAF = window.requestAnimationFrame || window.webkitRequestAnimationFrame
     rAF(function vecframe() {
+      //the order is: clear - vector - render
+      vm.setramblk(vramOffset, new Uint8Array(vramSize))
       vm.triggerVector(0)
       renderScreen()
       if(vm.active)