Add H264 profile to webrtc::VideoCodecH264 and webrtc::VideoPayload

It's necessary to check H264 profile information as well as payload name
in PayloadIsCompatible in RTPPayloadRegistry.

BUG=webrtc:6743

Review-Url: https://codereview.webrtc.org/2525693003
Cr-Commit-Position: refs/heads/master@{#15248}

webrtc/modules/video_coding/codec_database.cc

@@ -68,6 +68,7 @@ VideoCodecH264 VideoEncoder::GetDefaultH264Settings() {
   h264_settings.spsLen = 0;
   h264_settings.ppsData = nullptr;
   h264_settings.ppsLen = 0;
+  h264_settings.profile = H264::kProfileConstrainedBaseline;
 
   return h264_settings;
 }