Roll engine 804dca62a17c..6b8c150639b5 (3 commits) (#49908)

https://github.com/flutter/engine/compare/804dca62a17c...6b8c150639b5

git log 804dca62a17c..6b8c150639b5 --first-parent --oneline
2020-01-31 gw280@google.com Use static constexpr for iphone_xs_times (flutter/engine#16264)
2020-01-31 30870216+gaaclarke@users.noreply.github.com Started coalescing updates to viewport metrics after foregrounding the app. (flutter/engine#16270)
2020-01-31 chinmaygarde@google.com Remove superfluous INFO logs from //flutter/runtime. (flutter/engine#16280)


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 cbracken@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

-804dca62a17ca3bea4b508bc622218f88cfcd78f
+6b8c150639b5821a59eb5494031648a6a3095507