Roll engine 70f21b0edb06..99092a0436a2 (4 commits) (#40970)

git@github.com:flutter/engine.git/compare/70f21b0edb06...99092a0436a2

git log 70f21b0edb06..99092a0436a2 --no-merges --oneline
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia be0d7dfa6194..9a9841178078 (2 commits) (flutter/engine#12368)
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia e5b65d212bca..be0d7dfa6194 (3 commits) (flutter/engine#12367)
2019-09-20 liyuqian@google.com Revert "Reland "Smooth out iOS irregular input events delivery (#11817)" (#12280)" (flutter/engine#12364)
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia f47717ad8cc7..e5b65d212bca (4 commits) (flutter/engine#12366)


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 stuartmorgan@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

bin/internal/engine.version

-70f21b0edb0636fac38127b49064d03beb0a1ed8
+99092a0436a2dd3f1228ffe8818055fbf72b3eec