Roll Flutter from ee86e61f73ea to 37a1aaf8c11a (4 revisions) (#970)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index af28863..23347b6 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-ee86e61f73ea5a6880eef377febc3f2c37f1b2f6
+37a1aaf8c11a2963f066427089d8dd3709a4a48d