Roll Flutter from f3717d70d7d2 to 78e3b93664c7 (24 revisions) (#2310)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index 4617101..b0a8d03 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-f3717d70d7d2660ed830835c8ee33a01af71ce08
+78e3b93664c7784d806fe00080bd800f30cec662