Added 8 new vr layout tests for various requestPresent conditions

third_party/WebKit/LayoutTests/vr/resources/presentation-setup.js

+var webgl2 = false;
 var webglCanvas = document.getElementById("webgl-canvas");
+if (!webglCanvas) {
+  webglCanvas = document.getElementById("webgl2-canvas");
+  webgl2 = true;
+}
 var glAttributes = {
   alpha : false,
   antialias : false,
 };
-var gl = webglCanvas.getContext("webgl", glAttributes);
+var gl = webglCanvas.getContext(webgl2 ? "webgl2" : "webgl", glAttributes);
 
 function runWithUserGesture(fn) {
   function thunk() {
     document.removeEventListener("keypress", thunk, false);
     fn()
   }
   document.addEventListener("keypress", thunk, false);
   eventSender.keyDown(" ", []);
 }