Reland "Improve counterscroll handling" The relands commit c3a63721ee0613b73066c5166109c0dd054b926e (reverted in 065a4adfb51b2d40aa2269673cc19e504ca42ffd). The original CL was reverted because of CLS benchmark regressions (crbug.com/1186894) for the cases described in crbug.com/1187979. This reland changes code to make it backward compatible with the original code for the cases. The original CL also caused some layout benchmark regressions (crbug.com/1186933) because of the added MapRect operations. This CL removes the MapRect operations because the checks of unmapped starting points already suffice. Original change's description: > Improve counterscroll handling > > Previously we tracked the maximum scroll offset in a viewport to ignore > counterscroll shifts, but it failed when > - There were multiple scrollers scroll at the same time. Tested by > external/wpt/layout-instability/shift-with-counterscroll-2.html. > - An invisible shift was countered by both scroll and transform, e.g. > move layout location by 100px, scroll by -50px, and transform by > -50px. Tested by > external/wpt/layout-instability/shift-with-counter-scroll-and-transform.html > > Now let PaintPropertyTreeBuilder track scroll delta, and pass the delta > to LayoutShiftTracker. > > Bug: 1182213 > Change-Id: I18366ff7bc0e96374a954bee1c1600b582681dd8 > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2741240 > Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org> > Reviewed-by: Chris Harrelson <chrishtr@chromium.org> > Reviewed-by: Steve Kobes <skobes@chromium.org> > Cr-Commit-Position: refs/heads/master@{#861702} Bug: 1182213 Change-Id: I0ea8362d884ae7fd197001f2c1b658f0bb726820 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2754969 Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org> Reviewed-by: Steve Kobes <skobes@chromium.org> Cr-Commit-Position: refs/heads/master@{#862955} diff --git a/layout-instability/shift-with-counterscroll-2.html b/layout-instability/shift-with-counterscroll-2.html new file mode 100644 index 0000000..d997230 --- /dev/null +++ b/layout-instability/shift-with-counterscroll-2.html
@@ -0,0 +1,59 @@ +<!DOCTYPE html> +<title>Layout Instability: shift with counterscroll not counted, with 2 scrollers</title> +<link rel="help" href="https://wicg.github.io/layout-instability/" /> +<style> +.scroller { + overflow: scroll; + position: absolute; + left: 20px; + top: 20px; + width: 200px; + height: 200px; +} +.content { + width: 170px; + height: 600px; +} +.changer { + position: relative; + background: yellow; + left: 10px; + top: 100px; + width: 150px; + height: 150px; +} + +</style> +<div id="scroller1" class="scroller"> + <div class="content"> + <div id="changer1" class="changer"></div> + </div> +</div> +<div id="scroller2" class="scroller"> + <div class="content"> + <div id="changer2" class="changer"></div> + </div> +</div> +<script src="/resources/testharness.js"></script> +<script src="/resources/testharnessreport.js"></script> +<script src="resources/util.js"></script> +<script> + +promise_test(async () => { + const watcher = new ScoreWatcher; + + // Wait for the initial render to complete. + await waitForAnimationFrames(2); + + // Top goes from 100 to 200. scroll by 100 to counter it. + changer1.style.top = "200px"; + scroller1.scrollTop = 100; + // Top goes from 100 to 300. scroll by 200 to counter it. + changer2.style.top = "300px"; + scroller2.scrollTop = 200; + + await waitForAnimationFrames(3); + assert_equals(watcher.score, 0); +}, "Shift with counterscroll not counted, with 2 scrollers."); + +</script> 