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`.
We currently fire the change event on <input> elements when they lose
focus. The spec allows for us to also fire the event when changes are
"committed", so long as such an action makes sense for the input type.
This patch detects when the return key is entered in an <input> element
and uses that as the commit action for text-related types. If no change
has occurred since the last commit, no change event is fired.
