This follows the spec by introducing a new "Placeholder" canvas context
mode. The underlying offscreen canvas is kept accessible from the DOM
element to allow for the drawImage() implementation to work with canvases
that have transfered their control.
Signed-off-by: webbeef <me@webbeef.org>
This refactors some of the code that is shared with toDataURL, and
updates the webidl definition to match the current spec (using a default
value for the mime type).
Signed-off-by: webbeef <me@webbeef.org>
Extracted this out of #5649
This commit was created with the following commands:
```
find . -iname "*.webidl" -type f -print0 | xargs -0 sed -i '' 's/http:\(.*\)whatwg.org/https:\1whatwg.org/g'
```
```
find . -iname "*.rs" -type f -print0 | xargs -0 sed -i '' 's/http:\(.*\)whatwg.org/https:\1whatwg.org/g'
```
