Event Timing reports EventTarget for more pointer events

[chromium-wpt-export-bot]

Only in cases where there is not a single pointer event registered on a page, blink may entirely optimize out EventDispatch steps, since there are no observers anyway. This optimization should not normally be detectable.

However, the Event Timing API still measures these events and reports them to the performance timeline. Because the EventDispatch steps are where we assign EventTarget to Event objects, the Event Timing API was effectively missing the target value whenever we skipped this step.

This patch plumbs the original HitTest target which we fall back to under such situations.

Bug: 1367329
Change-Id: Icf21e6103c98261e9f6e88cef1ac09f3a683751b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5246848
Commit-Queue: Michal Mocny <mmocny@chromium.org>
Reviewed-by: Aoyuan Zuo <zuoaoyuan@chromium.org>
Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1255634}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.

[dev-ansung]

Unstable results

Test	Subtest	Results	Messages
/event-timing/duration-with-target-low.html		OK: 7/10, TIMEOUT: 3/10
/event-timing/duration-with-target-low.html	PerformanceObserver with durationThreshold of 300 and processingDelay of 0 doesn't see any entries in the observer	FAIL: 7/10, TIMEOUT: 3/10	assert_greater_than_equal: The entry's duration should be greater than or equal to 304 ms. expected a number greater than or equal to 304 but got 300;Test timed out;assert_greater_than_equal: The entry's duration should be greater than or equal to 304 ms. expected a number greater than or equal to 304 but got 301
/event-timing/interactionid-tap.html		OK: 1/10, TIMEOUT: 9/10
/event-timing/interactionid-tap.html	Event Timing: compare event timing interactionId for tap.	FAIL: 1/10, TIMEOUT: 9/10	assert_greater_than: Should have a non-trivial interactionId for pointerdown event expected a number but got a "undefined";Test timed out

[dev-ansung]

Filed https://crbug.com/1524539.
@KyleJu @DanielRyanSmith Could you please admin merge? Thanks