Currently, WebPageCompositor always turns off blending when compositing the "root" layer, regardless of whether it's drawn by the BackingStore or by an AC layer. This is PR159998.
Created attachment 145591 [details] Patch
I got an internal R+ from Jakob Petsovits, in a comment on the PR
Comment on attachment 145591 [details] Patch Looks good.
Created attachment 145608 [details] Patch Improved changelog message with PR number and credit to Jakob =)
Comment on attachment 145608 [details] Patch Even better :)
Comment on attachment 145608 [details] Patch Clearing flags on attachment: 145608 Committed r119718: <http://trac.webkit.org/changeset/119718>
All reviewed patches have been landed. Closing bug.