diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
index 654ea6b..e691220 100644
--- a/LayoutTests/ChangeLog
+++ b/LayoutTests/ChangeLog
@@ -1,3 +1,27 @@
+2019-10-17  Simon Fraser  <simon.fraser@apple.com>
+
+        REGRESSION (r243347) Layout tests fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on* are flakey
+        https://bugs.webkit.org/show_bug.cgi?id=203122
+        rdar://problem/50058173
+
+        Reviewed by Wenson Hsieh.
+        
+        Rewrite these tests to wait for scrolling to finish, since the overflow is now accelerated and we need
+        to wait for momentum to end.
+
+        Also have them use UIHelper, factoring a function to work with overflow as well as document scroll.
+
+        * fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block-expected.txt:
+        * fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block.html:
+        * fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document-expected.txt:
+        * fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document.html:
+        * resources/ui-helper.js:
+        (window.UIHelper.callFunctionAndWaitForEvent):
+        (window.UIHelper.callFunctionAndWaitForScrollToFinish):
+        (window.UIHelper.callFunctionAndWaitForTargetScrollToFinish.return.new.Promise):
+        (window.UIHelper.callFunctionAndWaitForTargetScrollToFinish):
+        (window.UIHelper.callFunctionAndWaitForScrollToFinish.return.new.Promise): Deleted.
+
 2019-10-17  Dean Jackson  <dino@apple.com>
 
         ctx.font = "" asserts in CSS parser
diff --git a/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block-expected.txt b/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block-expected.txt
index 202fe03..2c3ae17 100644
--- a/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block-expected.txt
+++ b/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block-expected.txt
@@ -13,7 +13,6 @@
 Received event touchstart at 50, 150
 Received event touchmove at 50, 50
 Received event touchend
-Dispatched Drag
 PASS window.scrollX is 0
 PASS window.scrollY is 0
 PASS document.documentElement.scrollTop is 0
diff --git a/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block.html b/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block.html
index 0084df4..94b2086 100644
--- a/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block.html
+++ b/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-block.html
@@ -1,13 +1,14 @@
 <!DOCTYPE html> <!-- webkit-test-runner [ internal:AsyncOverflowScrollingEnabled=true ] -->
 <html>
 <head>
+    <meta name="viewport" content="initial-scale=1">
+    <script src="../../../../resources/ui-helper.js"></script>
     <script src="../../../../resources/js-test-pre.js"></script>
     <style>
         body {
             margin: 0;
         }
     </style>
-    <meta name="viewport" content="initial-scale=1">
 </head>
 <body>
     <div id="eventTarget" style="overflow: scroll; height: 200px">
@@ -20,29 +21,9 @@
         description("Test scrolling on a block without -webkit-overflow-scrolling.");
         window.jsTestIsAsync = true;
 
-        function getDragUIScript(startX, startY, endX, endY)
+        async function runTest()
         {
-            return `
-            (function() {
-                uiController.dragFromPointToPoint(${startX}, ${startY}, ${endX}, ${endY}, 0.15, function() {
-                    uiController.uiScriptComplete("Dispatched Drag");
-                });
-            })();`
-        }
-
-        function runTest()
-        {
-            function scrollEventHandler(event) {
-                shouldBe("window.scrollX", "0");
-                shouldBe("window.scrollY", "0");
-                shouldBe("document.documentElement.scrollTop", "0");
-                shouldBe("document.documentElement.scrollLeft", "0");
-                shouldBeTrue("document.getElementById('eventTarget').scrollTop > 0");
-                shouldBe("document.getElementById('eventTarget').scrollLeft", "0");
-                finishJSTest();
-            }
             let eventTarget = document.getElementById("eventTarget");
-            eventTarget.addEventListener("scroll", scrollEventHandler);
 
             function touchEventHandler(event) {
                 if (event.touches.length)
@@ -55,18 +36,24 @@
             eventTarget.addEventListener('touchend', touchEventHandler, { 'passive': true });
             eventTarget.addEventListener('touchcancel', touchEventHandler, { 'passive': true });
 
-            if (window.testRunner) {
-                testRunner.runUIScript(getDragUIScript(50, 150, 50, 50), function(result) {
-                    debug(result);
-                });
-            }
-
             shouldBe("window.scrollX", "0");
             shouldBe("window.scrollY", "0");
             shouldBe("document.documentElement.scrollTop", "0");
             shouldBe("document.documentElement.scrollLeft", "0");
             shouldBe("document.getElementById('eventTarget').scrollTop", "0");
             shouldBe("document.getElementById('eventTarget').scrollLeft", "0");
+
+            await UIHelper.callFunctionAndWaitForTargetScrollToFinish(eventTarget, async () => {
+                await UIHelper.dragFromPointToPoint(50, 150, 50, 50, 0.15);
+            });
+
+            shouldBe("window.scrollX", "0");
+            shouldBe("window.scrollY", "0");
+            shouldBe("document.documentElement.scrollTop", "0");
+            shouldBe("document.documentElement.scrollLeft", "0");
+            shouldBeTrue("document.getElementById('eventTarget').scrollTop > 0");
+            shouldBe("document.getElementById('eventTarget').scrollLeft", "0");
+            finishJSTest();
         }
 
         window.addEventListener('load', runTest, false);
diff --git a/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document-expected.txt b/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document-expected.txt
index 202fe03..2c3ae17 100644
--- a/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document-expected.txt
+++ b/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document-expected.txt
@@ -13,7 +13,6 @@
 Received event touchstart at 50, 150
 Received event touchmove at 50, 50
 Received event touchend
-Dispatched Drag
 PASS window.scrollX is 0
 PASS window.scrollY is 0
 PASS document.documentElement.scrollTop is 0
diff --git a/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document.html b/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document.html
index 8acaf97..93615f8 100644
--- a/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document.html
+++ b/LayoutTests/fast/events/touch/ios/drag-block-without-overflow-scroll-and-passive-observer-on-document.html
@@ -1,13 +1,14 @@
 <!DOCTYPE html> <!-- webkit-test-runner [ internal:AsyncOverflowScrollingEnabled=true ] -->
 <html>
 <head>
+    <meta name="viewport" content="initial-scale=1">
     <script src="../../../../resources/js-test-pre.js"></script>
+    <script src="../../../../resources/ui-helper.js"></script>
     <style>
         body {
             margin: 0;
         }
     </style>
-    <meta name="viewport" content="initial-scale=1">
 </head>
 <body>
     <div id="eventTarget" style="overflow: scroll; height: 200px">
@@ -20,29 +21,9 @@
         description("Test scrolling on a block without -webkit-overflow-scrolling.");
         window.jsTestIsAsync = true;
 
-        function getDragUIScript(startX, startY, endX, endY)
+        async function runTest()
         {
-            return `
-            (function() {
-                uiController.dragFromPointToPoint(${startX}, ${startY}, ${endX}, ${endY}, 0.15, function() {
-                    uiController.uiScriptComplete("Dispatched Drag");
-                });
-            })();`
-        }
-
-        function runTest()
-        {
-            function scrollEventHandler(event) {
-                shouldBe("window.scrollX", "0");
-                shouldBe("window.scrollY", "0");
-                shouldBe("document.documentElement.scrollTop", "0");
-                shouldBe("document.documentElement.scrollLeft", "0");
-                shouldBeTrue("document.getElementById('eventTarget').scrollTop > 0");
-                shouldBe("document.getElementById('eventTarget').scrollLeft", "0");
-                finishJSTest();
-            }
             let eventTarget = document.getElementById("eventTarget");
-            eventTarget.addEventListener("scroll", scrollEventHandler);
 
             function touchEventHandler(event) {
                 if (event.touches.length)
@@ -50,23 +31,30 @@
                 else
                     debug("Received" + (event.cancelable ? " cancelable" : "") + " event " + event.type);
             }
+
             document.addEventListener('touchstart', touchEventHandler, { 'passive': true });
             document.addEventListener('touchmove', touchEventHandler, { 'passive': true });
             document.addEventListener('touchend', touchEventHandler, { 'passive': true });
             document.addEventListener('touchcancel', touchEventHandler, { 'passive': true });
 
-            if (window.testRunner) {
-                testRunner.runUIScript(getDragUIScript(50, 150, 50, 50), function(result) {
-                    debug(result);
-                });
-            }
-
             shouldBe("window.scrollX", "0");
             shouldBe("window.scrollY", "0");
             shouldBe("document.documentElement.scrollTop", "0");
             shouldBe("document.documentElement.scrollLeft", "0");
             shouldBe("document.getElementById('eventTarget').scrollTop", "0");
             shouldBe("document.getElementById('eventTarget').scrollLeft", "0");
+
+            await UIHelper.callFunctionAndWaitForTargetScrollToFinish(eventTarget, async () => {
+                await UIHelper.dragFromPointToPoint(50, 150, 50, 50, 0.15);
+            });
+
+            shouldBe("window.scrollX", "0");
+            shouldBe("window.scrollY", "0");
+            shouldBe("document.documentElement.scrollTop", "0");
+            shouldBe("document.documentElement.scrollLeft", "0");
+            shouldBeTrue("document.getElementById('eventTarget').scrollTop > 0");
+            shouldBe("document.getElementById('eventTarget').scrollLeft", "0");
+            finishJSTest();
         }
 
         window.addEventListener('load', runTest, false);
diff --git a/LayoutTests/resources/ui-helper.js b/LayoutTests/resources/ui-helper.js
index 5af9744..c010612 100644
--- a/LayoutTests/resources/ui-helper.js
+++ b/LayoutTests/resources/ui-helper.js
@@ -942,14 +942,18 @@
             target.addEventListener(eventName, resolve, { once: true });
             functionToCall();
         });
-
     }
 
     static callFunctionAndWaitForScrollToFinish(functionToCall, ...theArguments)
     {
+        return UIHelper.callFunctionAndWaitForTargetScrollToFinish(window, functionToCall, theArguments)
+    }
+
+    static callFunctionAndWaitForTargetScrollToFinish(scrollTarget, functionToCall, ...theArguments)
+    {
         return new Promise((resolved) => {
             function scrollDidFinish() {
-                window.removeEventListener("scroll", handleScroll, true);
+                scrollTarget.removeEventListener("scroll", handleScroll, true);
                 resolved();
             }
 
@@ -961,7 +965,7 @@
                 }
                 lastScrollTimerId = window.setTimeout(scrollDidFinish, 300); // Over 250ms to give some room for error.
             }
-            window.addEventListener("scroll", handleScroll, true);
+            scrollTarget.addEventListener("scroll", handleScroll, true);
 
             functionToCall.apply(this, theArguments);
         });