Roll Flutter from b3838eb3de6d to b5321d182a6b (1 revision) (#1743)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index e3f0de9..b287617 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-b3838eb3de6d10bfcd91ccca2d44b1939d625bb8
+b5321d182a6bf89fd3d86ceee52179867ffa7c89