Currently Skia version of GraphicsContext3D always uses BGRA8 format as source. It should check SK_x_SHIFT.
Created attachment 93779 [details] Patch
Comment on attachment 93779 [details] Patch Looks good. Thanks for taking care of this.
Comment on attachment 93779 [details] Patch Clearing flags on attachment: 93779 Committed r86679: <http://trac.webkit.org/changeset/86679>
All reviewed patches have been landed. Closing bug.