Fix some async repaint tests

LayoutTests/fast/repaint/resources/text-based-repaint.js

 // Asynchronous tests should manually call finishRepaintTest at the appropriate
 // time.
 window.testIsAsync = false;
 window.outputRepaintRects = true;
 
 function runRepaintTest()
 {
     if (!window.testRunner || !window.internals) {
         setTimeout(repaintTest, 500);
         return;
@@ skipping 30 matching lines @@
 function forceStyleRecalc()
 {
     if (document.body)
         document.body.offsetTop;
     else if (document.documentElement)
         document.documentElement.offsetTop;
 }
 
 function finishRepaintTest()
 {
+    if (!window.testRunner || !window.internals)
+        return;
+
     // Force a style recalc.
     forceStyleRecalc();
 
     var repaintRects = window.internals.layerTreeAsText(document, window.internals.LAYER_TREE_INCLUDES_REPAINT_RECTS);
 
     internals.stopTrackingRepaints(document);
 
     // Play nice with JS tests which may want to print out assert results.
     if (window.isJsTest)
         window.outputRepaintRects = false;
 
     if (window.outputRepaintRects)
         testRunner.setCustomTextOutput(repaintRects);
 
     if (window.afterTest)
         window.afterTest();
 
     // Play nice with async JS tests which want to notifyDone themselves.
     if (!window.jsTestIsAsync)
         testRunner.notifyDone();
 }