Roll engine 4f00cb745c28..c96f3536f316 (4 commits) (#38582)

git@github.com:flutter/engine.git/compare/4f00cb745c28...c96f3536f316

git log 4f00cb745c28..c96f3536f316 --no-merges --oneline
2019-08-14 dnfield@google.com Revert "Update README.md (#11007)" (flutter/engine#11009)
2019-08-14 dnfield@google.com Update README.md (flutter/engine#11007)
2019-08-14 bkonyi@google.com Roll src/third_party/dart c4727fddf4..e35e8833ee (1 commits)
2019-08-14 dnfield@google.com Drop firebase test from Cirrus (flutter/engine#11005)

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bin/internal/engine.version

-4f00cb745c2895feb47985725f8ada94df72ce36
+c96f3536f316c9c18a909c09fcc5cb70fc7f63d6