Roll Flutter from bc0ec85717de to 785513234141 (1 revision) (#1397)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index 1168be5..c8f1b52 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-bc0ec85717de14677a0253814faead368ac2abe8
+7855132341412214167c72189611e0c7c076fa30