Roll engine 4ee6489..a7e0e87 (8 commits)

flutter/engine@4ee6489...a7e0e87

git log 4ee6489..a7e0e87 --date=short --no-merges --format='%%ad %%ae %%s'
2018-08-17 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia 12d13ae7f4e6..c623af2e1044 (8 commits) (flutter/engine#6040)
2018-08-17 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia da135c397356..12d13ae7f4e6 (7 commits) (flutter/engine#6039)
2018-08-17 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia bc414ed5dec5..da135c397356 (1 commits) (flutter/engine#6038)
2018-08-16 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia e21f0ec04e98..bc414ed5dec5 (2 commits) (flutter/engine#6037)
2018-08-16 jamesderlin@users.noreply.github.com Fix potential null pointer dereference in FlutterDartProject (flutter/engine#6035)
2018-08-16 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia 8d77d1d85e2f..e21f0ec04e98 (5 commits) (flutter/engine#6036)
2018-08-16 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia cbb7d572aaa1..8d77d1d85e2f (12 commits) (flutter/engine#6034)
2018-08-16 37626415+skia-flutter-autoroll@users.noreply.github.com Roll src/third_party/skia cbd83bbd77d1..cbb7d572aaa1 (5 commits) (flutter/engine#6033)

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Author: engine-flutter-autoroll

bin/internal/engine.version

@@ -1 +1 @@
-4ee648914f91909d2153e2ee76a057d970b0512d
+a7e0e87ad687bacb5612005c71e5107177d79830