replace CSXformSteps::Required() in GrSurfaceContext

Calls to Required() are subtly error prone without taking the alpha
types into account.  Just so happens that we're doing half of that here
ourselves, and letting Required() handle the rest... best to just let
CSXformSteps handle all the logic.

This _does_ slightly_ change the values of unpremul and premul, in that
it's now possible for them both to be true when we need a color space
transform (when the source and dst are both premul).  We don't think
this actually changes any of the logic that uses these bools though...
the canvas2D fast paths are unchanged because if needsColorConversion is
false, we'll still never set both at once.  And the `convert` bool only
ever looks at the logical or of the two, so it won't change.

Change-Id: I051793cd84693e1a5dd367d036ab7f2e2308bbf8
Reviewed-by: Brian Osman <>
Commit-Queue: Mike Klein <>
1 file changed