--- a/layout/base/tests/test_scroll_snapping_scrollbars.html
+++ b/layout/base/tests/test_scroll_snapping_scrollbars.html
@@ -258,19 +258,23 @@ function doTest() {
 
   stopFrameCount = 0;
   waitForScrollStart();
 }
 
 function waitForScrollStart() {
   // Wait for up to 30 frames for scrolling to start
   var testCase = testCases[step];
-  if (testCase.startScroll.y != sc.scrollTop
-      || testCase.startScroll.x != sc.scrollLeft
-      || ++stopFrameCount < 30) {
+  if (++stopFrameCount > 30) {
+    ok(false,
+      "Step " + step + ": Frame count limit reached without scrolling." +
+      "(" + testCase.description + ")");
+    window.requestAnimationFrame(doMouseUp);
+  } else if (testCase.startScroll.y != sc.scrollTop
+             || testCase.startScroll.x != sc.scrollLeft) {
     window.requestAnimationFrame(doMouseUp);
   } else {
     window.requestAnimationFrame(waitForScrollStart);
   }
 }
 
 function doMouseUp() {
   var testCase = testCases[step];