When merging into an already chained op update the head's op bounds.

Also assert in GrRenderTargetOpList that chained ops' bounds are
contained in head op's bounds.

Change-Id: I70303ecfbb314d7d04d03f6ae6eae27e9956a7ce
Reviewed-on: https://skia-review.googlesource.com/154981
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
2 files changed