Roll Flutter from b62327903d31 to 919d20511cf6 (2 revisions) (#4871)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index 8169840..e152d93 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-b62327903d3190a50abd4b6c3693583f560285f3
+919d20511cf667d1dc0b8b4bac06b202b60af641