Documents created by DOMParser and fragment documents do not
have an origin set on the document by the spec. These documents
also happen to never become fully active.
By properly implementing the steps for the <img> element to only
update the image data for documents which are fully active, this
fixes a crash for img elements in these types of documents.
Unfortunately, this is not a full fix for the microtask queue case.
This is because it seems possible for node document for an <img>
element to be changed during the microtask queue for that document.
It is not clear to me how this can be fixed in a nice way.
Fixes at least three WPT test that were previously timing out:
- html/semantics/embedded-content/media-elements/error-codes/error.html
- html/semantics/embedded-content/media-elements/location-of-the-media-resource/currentSrc.html
- html/semantics/embedded-content/the-video-element/video_crash_empty_src.html
This commit begins to implement the track processing model. When the
`src` attribute is updated, we now fetch the given source file.
Currently, we always fire an `error` event once fetching is completed,
as we don't support processing the fetched data.
