Roll engine 5f61056..e164e83 (9 commits)

flutter/engine@5f61056...e164e83

git log 5f61056..e164e83 --no-merges --oneline
e164e83 Reset the raster cache when the compositor context is created. (flutter/engine#6150)
f02fc8c Dart SDK roll for 2018/09/06 (flutter/engine#6189)
58a1894 Update to latest clang (flutter/engine#6174)
9b297b3 Roll src/third_party/skia a9564d6dae1c..106d04e907c1 (7 commits) (flutter/engine#6190)
e70d0e1 Always serialize fonts during skp capturing (flutter/engine#6160)
bd7593b [fuchsia] Plumb root_surface_transformation in scene_update_context (flutter/engine#6187)
30c8da8 Pull $flutter_root:config into shell/engine/version:version (flutter/engine#6186)
a146862 Roll src/third_party/skia 33d3d31a7e28..a9564d6dae1c (5 commits) (flutter/engine#6185)
058edef Fix LibTxt/minikin text shifiting when breaking into multiple runs (flutter/engine#6184)

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Author: engine-flutter-autoroll

bin/internal/engine.version

@@ -1 +1 @@
-5f61056946efa1380f87c402f960be9e7b19cdc4
+e164e83a857fae541492ca810e3d731b39ff7ffd