Fix no_size_t_to_int_warning in rtp_rtcp:rtp_rtcp_format target

Change types in interface to plain int.
When putting values into raw buffer / structures with small types, use rtc::dchecked_cast.

BUG=webrtc:1348

Review-Url: https://codereview.webrtc.org/3013623002
Cr-Original-Commit-Position: refs/heads/master@{#19813}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 772bd8b6a7d232c94b1d2b1d37ec7e1f9515c7a7
6 files changed