Roll external/skia e19a4f261..e68b5bd4e (3 commits)

https://skia.googlesource.com/skia.git/+log/e19a4f261..e68b5bd4e

2019-07-29 csmartdalton@google.com don't try to format includes on windows
2019-07-29 csmartdalton@google.com Rename labrynth.cpp -> labyrinth.cpp
2019-07-29 senorblanco@chromium.org First draft of GrDawnBuffer.

The AutoRoll server is located here: https://skia-autoroll.corp.goog/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: Ic828d3844a343f2b0674a78106fc628791e930b1
Exempt-From-Owner-Approval: The autoroll bot does not require owner approval.