Guard AA change to wait for rebaselines

We use SK_SUPPORT_LEGACY_DELTA_AA to guard the golden image change.
Such flag is defined for Android, Chrome, and Google3 so our auto-rollers
should all be OK.

TBR: bungeman@google.com

Bug: skia:6947
Change-Id: Ic2705e82f4f7f15ec08499254dce75b93d41727e
Reviewed-on: https://skia-review.googlesource.com/33762
Reviewed-by: Yuqian Li <liyuqian@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
2 files changed