Roll engine 36b5b1936765..dfd281bcaefe (3 commits) (#39153)

git@github.com:flutter/engine.git/compare/36b5b1936765...dfd281bcaefe

git log 36b5b1936765..dfd281bcaefe --no-merges --oneline
2019-08-23 skia-flutter-autoroll@skia.org Roll src/third_party/skia 0f15d7373bf1..e8a2c8053daa (8 commits) (flutter/engine#11418)
2019-08-23 yjbanov@google.com Shrink cirrus docker image: reduce RUN count, apt-get clean (flutter/engine#11416)
2019-08-23 chinmaygarde@google.com Avoid root surface acquisition during custom composition with software renderer. (flutter/engine#11394)

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https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff (liyuqian@google.com), and stop
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