Add support for unsigned parameters in FieldTrialParser

Bug: webrtc:10932
Change-Id: I3f56244a6be532065e4096cf1a289e27a032bc44
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/150886
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29018}
diff --git a/rtc_base/experiments/struct_parameters_parser.h b/rtc_base/experiments/struct_parameters_parser.h
index b40f381..523ecfb 100644
--- a/rtc_base/experiments/struct_parameters_parser.h
+++ b/rtc_base/experiments/struct_parameters_parser.h
@@ -53,8 +53,10 @@
 extern template class TypedParser<bool>;
 extern template class TypedParser<double>;
 extern template class TypedParser<int>;
+extern template class TypedParser<unsigned>;
 extern template class TypedParser<absl::optional<double>>;
 extern template class TypedParser<absl::optional<int>>;
+extern template class TypedParser<absl::optional<unsigned>>;
 
 extern template class TypedParser<DataRate>;
 extern template class TypedParser<DataSize>;