Roll engine 179fab9..ed1557f (2 commits) (flutter#42402)

git@github.com:flutter/engine.git/compare/179fab9dcbac...ed1557f

git log 179fab9..ed1557f --no-merges --oneline
2019-10-10 chinmaygarde@google.com Don’t bump iOS deployment target for Metal builds. (flutter/engine#13051)
2019-10-10 duanweiwei1982@gmail.com Add texture support for macOS shell. (flutter/engine#8507)


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 chinmaygarde@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 @@
-179fab9dcbac3889390ab01bda6ab795dea43b61
+ed1557f82dd4cdb5477794ae7b2f3b9d55c53e40