January 2021 - Code Health, New Features, Testing and Stability Fixes

<td><td>Over 93% pass rate on the scroll timeline tests.</td></td>

<td><td>Over 350 passing tests.</td></td>

<td><td>Recent areas of development:</td></td>

    <td><td>Extended the scope of the polyfill:</td></td>

        <td><td>EventTarget</td></td>

        <td><td>Promises</td></td>

        <td><td>Tasks</td></td>

    <td><td>Support writing modes</td></td>

<td><td>The challenge is that size dependency could change while the
animation is running. And we need to catch the change and restart the
composited animation.</td></td>

<td><td>The feature is in common use. One can write CSS only animations
without the need to resort to JS for size calculation, such as the above
demo.</td></td>

<td><td>Recent spec <a
href="https://github.com/w3c/csswg-drafts/issues/4953">discussion</a>
decided that aspect ratios should be interpolated by the log of their value,
to preserve the same visual speed whether they are wide or narrow.</td></td>

<td><td>Setup infra for animating on the compositor thread.</td></td>

<td><td>Implement the interpolation logic.</td></td>

<td><td>Handle transition keyframes.</td></td>

<td><td>Handle multiple offsets in keyframes.</td></td>

<td><td>Implement main-thread fallback logic.</td></td>

<td><td>Finch experiment: 50% on canary + dev + beta.</td></td>

<td><td><a
href="https://groups.google.com/u/1/a/chromium.org/g/blink-dev/c/bta50W_Hg24">Intent
to ship</a> has been approved with 3 LGTMs.</td></td>

<td><td>Enabled for stable at 1% starting with M88.</td></td>

<td><td>Improvement of the feature is still on-going, such as the <a
href="https://bugs.chromium.org/p/chromium/issues/detail?id=1150979">simulated
clicks</a>.</td></td>

<td><td>Landed <a
href="https://bugs.chromium.org/p/chromium/issues/detail?id=1113863">scrolling
the &lt;select&gt; popup</a>.</td></td>

<td><td>Designed <a
href="https://docs.google.com/document/d/1w_Pr4sKPXfHz03ZUxVSZL23xjQy-TiKAKf8rmbcW1Fc/edit#">metrics</a>
for scroll unification and LGTMed by the metrics team.</td></td>

<td><td>Landed scroll bubbling from OOPIFs to ancestor frame</td></td>

<td><td>Schedule frames for popup widgets in tests using compositor
thread.</td></td>

Scroll timeline polyfill

Both kevers@ and flackr@ have been working extensively on this feature.

Compositing percentage based transforms

menu.hidden { transform: translateX(-100%) }

kevers@ re-enabled this feature in M89:

Aspect ratio interpolation

Demo Before Demo After

flackr@ implemented aspect ratio interpolation, and enabled it by default in M90.

Composite background-color animation

The above background-color animation demo runs on the compositor thread with the experimental flag. xidachen@ has made great progress on this feature, including:

Click/Auxclick as pointer event

liviutinta@ and mustaq@ co-worked on this feature and shipped it to stable. Here is the major work:

Capability delegation with payment request

mustaq@ built an initial prototype that allows PaymentRequest in subframe provided a token is passed into it. The PaymentRequest now consumes user activation.

Scroll unification

liviutinta@ kept working on this feature, and has made progress.

Scroll to images (and videos)

flackr@ has created and uploaded the explainer for this feature.

<td><td>Determine the root cause, landed the <a
href="https://chromium-review.googlesource.com/c/chromium/src/+/2488181">fix</a>
on ToT.</td></td>

<td><td>Merged the fix back to M88 and M89.</td></td>

Animation security fix: use after poison

kevers@ fixed a crash in Animatable::Animation. The problem is that running user code (JS) can result in the destruction of an execution context. We cannot simply check and forget about the execution context. The solution is to double check if the context is used downstream of script execution.

Float-cast-overflow in MouseEvent::PageX

liviutinta@ fixes a float-cast-overflow bug that is caused by static_cast<int>(double value) when the value is out of range. The solution is to usd std::trunc and clampToInt instead.

Paint worklet regression

Stable Canary

xidachen@ fixed a regression due to a misuse of hashmap. In the above demo, the same animation is applied to both elements. In other words, the animations of the two elements should be in sync. However, the stable version is wrong. The canary version has the fix in it, and it is correct.

Crash in PointerEventFactory

mustaq@ untangled a mixed-up crash report that becomes release-blocker-stable at the last moment. The effort of fixing the crash includes:

Paint worklet crash

xidachen@ fixed a crash where the root cause is that our code path hits a DCHECK that is no longer applicable. The solution is to remove the outdated DCHECK.

<td><td>Specifically, we closed more bugs than opened in P1 and P2
categories.</td></td>

<td><td>Our P1 and P2 bugs are less than 40% of total bugs.</td></td>

<td><td>~40% bugs have owners assigned.</td></td>

Chapter IV: Code Health

Our team had a great start to the year by closing over 70 bugs in this sprint:

girard@ collected our team bug data and generated graphs to visualize it.

girard@ re-enabled “MissedTOUCHEVENTF_UP” which tracks a hack in windows touch. We would like to tear out the hack/workaround once usage drops.

liviutinta@ removed the AzimuthAltitude flag since it has been turned on by default since M86.

lanwei@ and liviutinta@ fixed input failing tests on the new WPT bots.

mustaq@ landed Mouse/PointerEvent related code cleanup.