Roll engine f6af1f20ba92..74662ab69523 (13 commits) (#22599)

https://github.com/flutter/engine/compare/f6af1f20ba92...74662ab69523

git log f6af1f20ba92..74662ab69523 --no-merges --oneline
74662ab69 Revert "Share engine layers with the framework" (flutter/engine#6412)
2de87a80f Roll src/third_party/skia 6719fcc43b1e..deb512045e6a (7 commits) (flutter/engine#6411)
68a42e3f4 Add nullability annotations to MethodChannel/MethodCall. (flutter/engine#6393)
71ba20a64 Dart SDK roll for 2018-10-02 to d2c5a24fd9ead97a7f18d02786e679293cc3709e (flutter/engine#6410)
9ccc96625 Share engine layers with the framework (flutter/engine#6406)
fa719e3e7 Roll src/third_party/skia cc4dbfcfbd8a..6719fcc43b1e (17 commits) (flutter/engine#6409)
dc2634dcf Force lf-line endings for so that source offsets match across platforms. (flutter/engine#6408)
44a514943 Roll src/third_party/skia 7dae882574d2..cc4dbfcfbd8a (15 commits) (flutter/engine#6405)
de32c659b Roll src/third_party/skia 3b8b11e1f912..7dae882574d2 (15 commits) (flutter/engine#6403)
3a9c22afd Allow GetRectsForRange to provide more detailed/nuanced metrics through RectStyle enum. (flutter/engine#6335)
b59c86493 Rename the Android fragment support library JAR (flutter/engine#6400)
4213ac19c Add an Android fragment support library to third_party (flutter/engine#6384)
a785b25f4 do not count Hidden nodes at the beginning of the scrollable (flutter/engine#6381)

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bin/internal/engine.version

-f6af1f20ba92a819401d66ae4b2179b0775b0e12
+74662ab695238af0e7402f41c4bf9ad862bd37d2