Currently when the GPU cache is resized we allocate a new texture and
then copy the contents of the old texture to the new texture. This
copy requires either EXT_copy_image (for glCopyImageSubData) or
EXT_color_buffer_float (to bind the RGBAF32 texture to a framebuffer).
On devices where neither extension is supported, don't attempt to copy
the old texture. Instead mark the entire CPU-side copy of the cache as
dirty, meaning we will subsequently upload the entire contents to the
new texture. (A complete CPU-side copy is only mainted for the
PixelBuffer gpu cache bus type, not for Scatter ones. However, as the
Scatter type also requires EXT_color_buffer_float, we will only be in
this situation for PixelBuffer buses.)
Differential Revision: https://phabricator.services.mozilla.com/D103071
62eb49693e