Bug 1565053 [wpt PR 17671] - [FractionalScroll] Fix web tests, a=testonly

Automatic update from web-platform-tests
[FractionalScroll] Fix web tests

This CL fixes Blink web tests so that they pass when the Fractional
Scroll Offsets flag is enabled. This flag enables fractional offsets on
the Blink main thread which breaks some tests because they assume that
offsets will be floored.

I've modernized two tests:
fast/events/platform-wheelevent-paging-y-in-non-scrolling-div.html
fast/events/scale-and-scroll-div.html

The first appears to have been an issue with js-test modifying the page
while the second was passing but the PASS string in the -exected.txt
had changed to include the factional. Both tests now pass with and
without the feature enabled.

I removed fast/events/touch/gesture/touch-gesture-scroll-div-scaled.html
since it was testing the same thing as scale-and-scroll-div.html.

The rest of the tests required changing the layout such that it doesn't
cause us to land on fractional offsets (and thus the behavior will be
unchanged with and without the flag). Where this was difficult I just
allowed for approximate equality.

Bug: 414283
Change-Id: Ie03fa06b100fb9946675e921357c1eaebfe6a37e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1690293
Commit-Queue: David Bokan <bokan@chromium.org>
Reviewed-by: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676118}

--

wpt-commits: e93818b7c65d3bb3152ed5f7bf1f06019bd295bb
wpt-pr: 17671

testing/web-platform/tests/css/css-scroll-snap/snap-at-user-scroll-end-manual.html

@@ -6,7 +6,6 @@
 <style>
 body {
   margin: 0px;
-  overflow: scroll;
   scroll-snap-type: both mandatory;
 }
 #content {
@@ -22,6 +21,7 @@ body {
   width: 400px;
   height: 400px;
   background-color: lightblue;
+  overflow: hidden;
   scroll-snap-align: start;
 }
 #i1 {
@@ -74,10 +74,13 @@ button.onclick = function() {
   if (!scrolled_x || !scrolled_y)
     return;
 
-  assert_equals(window.scrollX, target.offsetLeft,
-        "window.scrollX should be at snapped position.");
-  assert_equals(window.scrollY, target.offsetTop,
-        "window.scrollY should be at snapped position.");
+  snap_test.step(() => {
+    assert_equals(window.scrollX, target.offsetLeft,
+          "window.scrollX should be at snapped position.");
+    assert_equals(window.scrollY, target.offsetTop,
+          "window.scrollY should be at snapped position.");
+  });
+
   // To make the test result visible.
   var content = document.getElementById("content");
   body.removeChild(content);