Roll Flutter Engine from fb99a84de07e to 6f5b6a37107b (2 revisions) (…

…#143183)

flutter/engine@fb99a84...6f5b6a3

2024-02-08 [email protected] [web] - Fix `inputmode` on Android Firefox (flutter/engine#46901)
2024-02-08 [email protected] [Impeller] Vulkan: Don't fail initialization if stencil-only textures aren't supported. (flutter/engine#50455)

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

To file a bug in Flutter: 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

bin/internal/engine.version

@@ -1 +1 @@
-fb99a84de07e556e3ec2d7a5cba6fcd758e61356
+6f5b6a37107bbe60d0b9ee3f8323bd3e3074ef68