Use construct/init pattern with GrPipeline to replace CreateAt.

Change-Id: Ic6c7432a9a298a143ce4f2431e94c89a0ea79793
Reviewed-on: https://skia-review.googlesource.com/8938
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
9 files changed