Add ScriptPromise::rejectWithDOMException

As [1] says, returning a Promise rejected with a DOMException is
a very common pattern and it is worth having a helper function for
the pattern.

[1]: https://github.com/w3ctag/promises-guide#rejection-reasons-should-be-errors

BUG=375021

Review URL: https://codereview.chromium.org/290983003

git-svn-id: svn://svn.chromium.org/blink/trunk@174646 bbb929c8-8fbe-4397-9dbb-9b2b20218538