dcsctp: Use correct field width for PPID

When migrating to use StrongAlias types, the PPID was incorrectly
modeled as an uint16_t instead of a uint32_t, as it was prior to using
StrongAlias. Most likely a copy-paste error from StreamID.

As the Data Channel PPIDs are in the range of 51-57, it was never caught
in tests.

Bug: webrtc:12614
Change-Id: I2b61ef7935df1222068e7f4e70fc2aaa532dcf7b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/214960
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33687}
diff --git a/net/dcsctp/public/types.h b/net/dcsctp/public/types.h
index 31c3f94..0b22fa8 100644
--- a/net/dcsctp/public/types.h
+++ b/net/dcsctp/public/types.h
@@ -19,7 +19,7 @@
 using StreamID = StrongAlias<class StreamIDTag, uint16_t>;
 
 // Payload Protocol Identifier (PPID)
-using PPID = StrongAlias<class PPIDTag, uint16_t>;
+using PPID = StrongAlias<class PPIDTag, uint32_t>;
 
 // Timeout Identifier
 using TimeoutID = StrongAlias<class TimeoutTag, uint64_t>;