For example, in the following abbreviated test HTML:
<span>some text</span>
<script>println("whf")</script>
We would have to craft the expectation file to include the "some text"
segment, usually with some leading whitespace. This is a bit annoying,
and makes it difficult to manually craft expectation files.
So instead of comparing the expectation against the entire DOM inner
text, we now send the inner text of just the <pre> element containing
the test output when we invoke `internals.signalTextTestIsDone`.
Change 'dom_node_for_event_dispatch' to locate the closest layout node
with a DOM node instead of only checking the direct ancestor.
This fixes hit-testing for buttons because they are wrapped into
multiple anonymous layout nodes (internally we use flex formatting for
them).
