47991fe12 Roll src/third_party/skia 2cb1315d99e4..cb52badca04a (5 commits) (flutter/engine#12293) (#40553)

git@github.com:flutter/engine.git/compare/31e5149a805b...47991fe122d9

git log 31e5149a805b..47991fe122d9 --no-merges --oneline
2019-09-16 skia-flutter-autoroll@skia.org Roll src/third_party/skia 2cb1315d99e4..cb52badca04a (5 commits) (flutter/engine#12293)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC jimgraham@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

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