was still just using a single vertex buffer that it allocates
upfront---and a tiny buffer---just big enough for a single rectangle
for a single composite operation. And so the driver was waiting for
-each composite operation to finish before reusing the bugger. And the
+each composite operation to finish before reusing the buffer. And the
change to GEM had made this problem even more noticeable. And Eric
even had a partially-working patch to fix this---simply allocating a
much larger vertex buffer and only doing the sync when wrapping around