Roll engine 4893b07..aaf4a9a (10 commits)

flutter/engine@4893b07...aaf4a9a

git log 4893b07..aaf4a9a --date=short --no-merges --format='%%ad %%ae %%s'
2018-08-03 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia 4c3b63e289c5..71fe8baccc01 (3 commits) (flutter/engine#5940)
2018-08-03 liyuqian@google.com Call drawPaint instead of drawPath if there's clip (flutter/engine#5937)
2018-08-03 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia cdfa16d086b8..4c3b63e289c5 (9 commits) (flutter/engine#5936)
2018-08-03 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia 1400d38e0863..cdfa16d086b8 (10 commits) (flutter/engine#5934)
2018-08-03 amirh@users.noreply.github.com Flush all embedded Android views on hot restart. (flutter/engine#5929)
2018-08-03 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia 578ef2847b72..1400d38e0863 (7 commits) (flutter/engine#5933)
2018-08-02 amirh@users.noreply.github.com Don't drop MotionEvents with unknown tool type. (flutter/engine#5931)
2018-08-02 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia 64cc576b1fa7..578ef2847b72 (20 commits) (flutter/engine#5930)
2018-08-02 regis@google.com Roll Dart to b04def964c428ada007cca7ef6b4936001db965d (flutter/engine#5928)
2018-08-02 jamesderlin@users.noreply.github.com Add an explicit `-[FlutterViewController init]` implementation (flutter/engine#5924)

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bin/internal/engine.version

@@ -1 +1 @@
-4893b0760df08cecd8ee97bdf03856c296a6df14
+aaf4a9a248369702ccd0aba8c2593c23b4602edd