In http://trac.webkit.org/changeset/91870, I added a lockPixels() call to ImageBuffer[Skia]::draw() in order to fix printing, which draws from accelerated->non-accelerated contexts.
However, this causes a readback even in the accelerated->accelerated case, causing a performance slowdown.
Created attachment 102680 [details]
Comment on attachment 102680 [details]
Committed r92227: <http://trac.webkit.org/changeset/92227>