This also adds a patch to flutter/flutter to fix head-head-head
configuration (until engine is rolled into framework again).
Change-Id: I6dae0983126a6664337834d3c93f1369139f1ac1
Reviewed-on: https://dart-review.googlesource.com/c/91922
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Jonas Termansen <sortie@google.com>