Web updates

HTML d28a66a8df60

Fix toBlob() and convertToBlob() In particular: * Neither method dealt properly with "serialization of a the bitmap as a file" returning null. * Neither method clearly indicated what had to happen synchronously (bitmap copy) and asynchronously (converting to a file). * toBlob() did not indicate the Realm of the new Blob object. * toBlob() invoked IDL's callback concept incorrectly. * convertToBlob() was weird with in parallel and queue a task. * convertToBlob() did not list a task source. Fixes #3386.

Anne van Kesteren

HTML e0383f683428

Throw when <canvas> is not usable as image This algorithm is used by createPattern() for which Chrome, Edge (different exception), Firefox, and Safari all throw. It's also used by drawImage() for which Edge, Firefox, and Safari throw. Chrome is the odd one out there. This changed in 76782de56908f4e2fd1127a5e5e279d622226e60 and nobody picked it up then. That change also forgot to change the domintro boxes which still suggest throwing (and how I noticed this problem).

Anne van Kesteren