Roll external/skia be852e44e..32f12aca3 (6 commits)

https://skia.googlesource.com/skia.git/+log/be852e44e..32f12aca3

2018-09-20 mtklein@google.com roll zilb
2018-09-20 mtklein@google.com remove pin in SkColor4f::premul()
2018-09-20 hcm@google.com progress on canvaskit page
2018-09-20 benjaminwagner@google.com Fix bzl missing include dir.
2018-09-20 benjaminwagner@google.com Fix bzl formatting.
2018-09-20 bungeman@google.com Properly align inside GrTextBlob.

The AutoRoll server is located here: https://autoroll-internal.skia.org/r/android-master-autoroll

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: I04b0e7ed9a40ba219cdc3aa5647503337dea73ab
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.