Roll fuchsia/sdk/core/mac-amd64 from W9PBe... to T3Xkz... (#13112)

Roll fuchsia/sdk/core/mac-amd64 from W9PBe... to T3Xkz...

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/fuchsia-mac-sdk-flutter-engine
Please CC  on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

https://dart.googlesource.com/external/github.com/flutter/engine/+/99a047dd25ce3ef4cf6504dd5b900495d2cbd2f4
diff --git a/commits.json b/commits.json
index 9f25829..c4bb225 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
-  "external/github.com/flutter/engine":"7fc960ea74787f3a1ec8b12937570eacce67c698",
+  "external/github.com/flutter/engine":"99a047dd25ce3ef4cf6504dd5b900495d2cbd2f4",
   "external/github.com/flutter/flutter":"3fea2838df051e99b2f72127a7d950287e522d0b",
   "sdk":"1e3cbd434472a79e73313795a55f094a1e9df0d4"
 }
\ No newline at end of file