This fix has landed in WR, but WR can't be updated right now, due
to a scroll change landing in WR without the Servo PR being ready
quite yet.
Fixes#14061.
Fixes#14073.
This updates webrender to include the webgl related changes
needed for this patch. There was an additional commit in
webrender before these landed, so also copy the shaders
for that change across. There is an interface change to
webrender push_image. For now, just pass zero, which is a
no-op to this function. A follow up commit will introduce
the servo specific changes to use this new interface.
