Roll Flutter from 37a1aaf8c11a to 83a88058d695 (6 revisions) (#974)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index 23347b6..39c1071 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-37a1aaf8c11a2963f066427089d8dd3709a4a48d
+83a88058d695762e920a5f309b208f02f3d57791