Make required dictionary members non-nullable again
These were changed to non-nullable to preserve existing behavior.
Because they are required, the risk here is that developers have noticed
they were required but successfully found and used the null loophole. At
the slightest sign of trouble with any of these, it should be reverted
and perhaps the specs should be changed to allow null.
BlobEvent test will be imported from:
https://github.com/w3c/web-platform-tests/pull/3749
PresentationConnectionAvailableEvent is untested:
https://crbug.com/648922
BUG=647693
Review-Url: https://codereview.chromium.org/2347473005
Cr-Commit-Position: refs/heads/master@{#420285}
12 files changed
