Fix SwizzleFragmentProcessor::constantOutputForConstantInput

Tracked this down as the source of failing tests in an unrelated CL.

Change-Id: I1427853a258596fdb658a5263683d3fb370bb353
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/388056
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
1 file changed