Roll engine d1692d4..6a96417 (4 commits) (flutter#40721)

git@github.com:flutter/engine.git/compare/d1692d4cc703...6a96417

git log d1692d4..6a96417 --no-merges --oneline
2019-09-17 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/linux-amd64 from RRgw-... to F-g18... (flutter/engine#12326)
2019-09-17 chinmaygarde@google.com Account for root surface transformation on the surfaces managed by the external view embedder. (flutter/engine#11384)
2019-09-17 matthew-carroll@users.noreply.github.com Introduce FlutterFragmentActivity (flutter/engine#12305)
2019-09-17 chinmaygarde@google.com Shuffle test order and repeat test runs once. (flutter/engine#12275)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC stuartmorgan@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

bin/internal/engine.version

@@ -1 +1 @@
-d1692d4cc703cc72ac2633d39df8e25ceaaa189d
+6a96417416b4a887a2041756ff7cc1cbef30a535