Roll Dart Protobuf Support from 9cf05f6e9f53 to 8337a7910fef (2 revisions)

https://dart.googlesource.com/protobuf/+log/9cf05f6e9f53..8337a7910fef

2022-08-22 omersa@google.com Rename _reportTruncatedMessage -> _throwTruncatedMessageError (#737)
2022-08-22 omersa@google.com Add GrpcServiceName annotation to gRPC classes (#733)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-protobuf-dart-sdk
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is aware of the problem.

To file a bug in Dart Protobuf Support: https://github.com/dart-lang/protobuf/issues
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Tbr: dart-ecosystem-gardener@grotations.appspotmail.com
Change-Id: Idc3d5a834fb6c9f08a73b11a4b1ac3b889001282
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/255842
Reviewed-by: Nate Bosch <nbosch@google.com>
Commit-Queue: Nate Bosch <nbosch@google.com>

DEPS

@@ -135,7 +135,7 @@ vars = {
   "path_rev": "9955b27b9bb98d87591208e19eb01c51d29fd467",
   "ply_rev": "604b32590ffad5cbb82e4afef1d305512d06ae93",
   "pool_rev": "fa84ddd0e39f45bf3f09dcc5d6b9fbdda7820fef",
-  "protobuf_rev": "9cf05f6e9f53d88b4b6c1f6f1accec09bcd5cca7",
+  "protobuf_rev": "8337a7910fef805214e5aae35a98abd481d87a18",
   "pub_rev": "ac7db6c07318efa4a8712110275eaf70f96a6d00", # manually rev'd
   "pub_semver_rev": "9fd28757ba45961ac5449e0f2b0020670e921475",
   "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",