Bug 661816 - Disable failing part of browser_awesomescreen.js test [r=mfinkle]

mobile/chrome/tests/browser_awesomescreen.js

@@ -413,6 +413,7 @@ gTests.push({
   },
 
   onCompositionEnd: function() {
+    /* TODO: This is currently failing (bug 642771)
     gCurrentTest._checkState();
 
     let isHiddenHeader = function() {
@@ -424,7 +425,6 @@ gTests.push({
     // but I don't have a better idea about how to do it for now since we don't
     // that to happen!
 
-    /* TODO: This is currently failing (bug 642771)
     waitForAndContinue(function() {
       gCurrentTest._checkState();
       runNextTest();