Bug 1685542 [wpt PR 27077] - Reload embed elements when url attribute is changed...

Bug 1685542 [wpt PR 27077] - Reload embed elements when url attribute is changed, a=testonly

Automatic update from web-platform-tests
Reload embed elements when url attribute is changed

Before this patch, the embed element gets reloaded when the url
attribute is changed only if there is a type attribute present, and
there is a comment on the type attribute check added in crrev.com/428661
saying that it is used to check if the embed element can transition from
"potentially active" to "active."

The spec[1] says that "whenever a potentially active embed element that
is remaining potentially active and has its src attribute set, changed,
or removed or its type attribute set, changed, or removed, the user
agent must queue an element task on the embed task source given the
element to run the embed element setup steps for that element."

The "potentially active" definition in the spec says that the element is
potentially active if "the element has either a src attribute set or a
type attribute set (or both)," and there is no suggestion that a type
attribute is *required* in order for the embed element to be potentially
active, so removing the type attribute check should align with the spec.

I made a UseCounter [2] to see if changing the src attribute without a type
attribute is something done frequently, and I found that 0.00006% of
page loads do so, which seems low enough to change this behavior.

[1] https://html.spec.whatwg.org/multipage/iframe-embed-object.html#the-embed-element
[2] https://chromestatus.com/metrics/feature/timeline/popularity/3749

Bug: 69648
Fixed: 1035330
Change-Id: I72c473d36a0bbe7980ba9a4b0530ef37fdef1a1d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2607807
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Reviewed-by: Mason Freed <masonf@chromium.org>
Cr-Commit-Position: refs/heads/master@{#868777}

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wpt-commits: c6d0f1bdc66eee70e9af12dcf960fb2ea3f1ac92
wpt-pr: 27077