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`.
The main issues are using Structured{Serialize,Deserailize} instead of
Structured{Serialize,Deserialize}WithTransfer and the temporary
execution context usage for StructuredDeserialize.
Allows Discord to load once again, as it uses a postMessage scheduler
to render components, including the main App component. The callback
checked the (previously) non-existent source attribute of the
MessageEvent and returned if it was not the main window.
Fixes the Twitch cookie consent banner saying "failed integrity check"
for unknown reasons, but presumably related to the source and origin
attributes.
