Roll Flutter from 53771aba0cd7 to a0abb7e89e1b (8 revisions) (#608)

diff --git a/.ci/flutter_master.version b/.ci/flutter_master.version
index 3d6d9cc..1796f45 100644
--- a/.ci/flutter_master.version
+++ b/.ci/flutter_master.version
@@ -1 +1 @@
-53771aba0cd73bca8b7211a16aa5a69f13304eaf
+a0abb7e89e1b5f2b5996110b523a66e56a774eb5