Fix flake in threaded CSSOM smooth scroll layout tests

LayoutTests/fast/scroll-behavior/resources/scroll-interruption-test.js

 // A SmoothScrollInterruptionTest verifies that in-progress smooth scrolls
 // stop when interrupted by an instant scroll, another smooth scroll, a
 // touch scroll, or a mouse wheel scroll.
 //
 // The only SmoothScrollInerruptionTest method that should be called by
 // outside code is run().
 //
 // Creates a SmoothScrollInterruptionTest with arguments:
 // scrollElement - Element being scrolled.
 // innerPoint - Absolute position (expressed as a dictionary with x and y fields)
@@ skipping 57 matching lines @@
 
     window.requestAnimationFrame(this.waitForSmoothScrollStart.bind(this));
 }
 
 SmoothScrollInterruptionTest.prototype.waitForSmoothScrollStart = function() {
     if (this.scrollElement.scrollTop == this.scrollStartPoint) {
         window.requestAnimationFrame(this.waitForSmoothScrollStart.bind(this));
         return;
     }
 
-    var scrollElement = this.scrollElement;
-    var scrollEndPoint = this.scrollEndPoint;
-    this.asyncTest.step(function() {
-        assert_not_equals(scrollElement.scrollTop, scrollEndPoint);
-    });
-
     var testCase = this.testCases[this.currentTestCase];
     testCase.interruptSmoothScroll(this);
     window.requestAnimationFrame(testCase.verifyScrollInterrupted.bind(testCase, this, this.testCaseComplete.bind(this)));
 }
 
 SmoothScrollInterruptionTest.prototype.testCaseComplete = function() {
     this.asyncTest.done();
 
     this.currentTestCase++;
     this.startNextTestCase();
@@ skipping 46 matching lines @@
     smoothScrollTest.asyncTest.step(function() {
         assert_not_equals(smoothScrollTest.scrollElement.scrollTop, smoothScrollTest.scrollNewEndpoint);
     });
 
     this.scrollInterruptionPoint = smoothScrollTest.scrollElement.scrollTop;
 }
 
 function verifyScrollInterruptedBySmoothScroll(smoothScrollTest, verificationComplete) {
     var currentPosition = smoothScrollTest.scrollElement.scrollTop;
 
-    if (currentPosition < this.scrollInterruptionPoint && currentPosition > smoothScrollTest.scrollNewEndpoint) {
+    if (currentPosition < this.scrollInterruptionPoint && currentPosition >= smoothScrollTest.scrollNewEndpoint) {
         verificationComplete();
     } else {
         window.requestAnimationFrame(this.verifyScrollInterrupted.bind(this, smoothScrollTest, verificationComplete));
     }
 }
 
 function interruptWithTouchScroll(smoothScrollTest) {
     if (window.eventSender) {
         window.eventSender.gestureScrollBegin(smoothScrollTest.innerPoint.x, smoothScrollTest.innerPoint.y);
         window.eventSender.gestureScrollUpdate(0, -10);
@@ skipping 28 matching lines @@
 }
 
 function interruptWithWheelScroll(smoothScrollTest) {
     if (window.eventSender) {
         window.eventSender.mouseMoveTo(smoothScrollTest.innerPoint.x, smoothScrollTest.innerPoint.y);
         window.eventSender.mouseScrollBy(0, -10);
     } else {
         document.write("This test does not work in manual mode.");
     }
 }