Roll external/skia f2e316c7e..4dc5a4540 (4 commits)

https://skia.googlesource.com/skia.git/+log/f2e316c7e..4dc5a4540

2018-05-21 caryclark@skia.org remove defines and add commas
2018-05-21 skia-recreate-skps@skia-swarming-bots.iam.gserviceaccount.com Update SKP version
2018-05-21 herb@google.com Add SkMakeUnique to gn
2018-05-21 jvanverth@google.com Disable perspective for emoji fallback

The AutoRoll server is located here: https://android-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.

Test: Presubmit checks will test this change.
Change-Id: I3a1de81478d63171852f627d09308e367befdbda
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.