Make createImageBitmap support SVG, but not RenderingContexts

[junov]

This change fixes issue #923 by allowing ImageBitmap objects to
be created from SVG source images, as long as the image has an
intrinsic size. If the image does not have an intrinsic size,
we still reject the promise with an InvalidStateError, as before.

This change also removes CanvasRenderingContext2D from
ImageBtimapSource, which was an oversight in PR #790. Since there
is no longer a concept of a standalone context, this is no longer
needed.

[annevk]

Could you add <span>SVG <code>image</code></span> element here while you're at it?

[zcorpan]

(markup typo in your comment?)

[annevk]

Fixed.

[annevk]

LGTM with that nit.

[junov]

New commit with nit addressed.

[annevk]

Landed as 43ad288.

[annevk]

Thank you!

[sebinsua]

This monkey patch by @Kaiido implies that "SVG image in Blob as source" isn't supported in Chrome yet and this appears to be the case with my own testing.

Am I misunderstanding things?

Is this tracked as a bug somewhere? It's been 8 years since this was merged.

[Kaiido]

Yes, no browser supports it currently, and I believe that at least in Worker scope it's admitted that we'll never have it because that would mean to move the DOM there.
Might be worth removing it from the specs entirely indeed.

For the ones that really want a bitmap version of an svg Blob, it's still possible through the blob: URL + <img> route, even if that's a bit convoluted:

if (blob.type === "image/svg+xml") {
  const img = new Image();
  img.src = URL.createObjectURL(blob);
  await img.decode();
  URL.revokeObjectURL(img.src);
  return createImageBitmap(img);
}