If an external image shows up multiple times while using a different image rendering
setting on each instance, we can erroneously call handler.lock() for each instance in
parallel, thus defaulting to the last image rendering setting supplied for all instances
in that batch.
To work around this, we get rid of the concept of having RenderTextureHosts maintain and
set the image rendering state, which results in a nice simplification. Then, when we go
to actually bind an external image inside WebRender, we set the image rendering state
at that point, so that regardless of how many instances of an external image are locked
simultaneously, we always use the correct image rendering setting for a batch.
Differential Revision: https://phabricator.services.mozilla.com/D158920
cfb26bdf6f