Roll Flutter (stable) from ac4e799d2370 to 9f455d2486bc (4 revisions) (#10208)

https://github.com/flutter/flutter/compare/ac4e799d2370...9f455d2486bc

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-stable-packages
Please CC muhatashim@google.com,stuartmorgan@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Flutter (stable): https://github.com/flutter/flutter/issues/new/choose
To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
diff --git a/.ci/flutter_stable.version b/.ci/flutter_stable.version
index 1cb5d9f..dd73f2e 100644
--- a/.ci/flutter_stable.version
+++ b/.ci/flutter_stable.version
@@ -1 +1 @@
-ac4e799d237041cf905519190471f657b657155a
+9f455d2486bcb28cad87b062475f42edc959f636