Implement RTCMediaSourceStats and friends in standard getStats().

This implements RTCAudioSourceStats and RTCVideoSourceStats, both
inheriting from abstract dictionary RTCMediaSourceStats:
https://w3c.github.io/webrtc-stats/#dom-rtcmediasourcestats

All members are implemented except for the total "frames" counter:
- trackIdentifier
- kind
- width
- height
- framesPerSecond

This means to make googFrameWidthInput, googFrameHeightInput and
googFrameRateInput obsolete.

Implemented using the same code path as the goog stats, there are
some minor bugs that should be fixed in the future, but not this CL:
1. We create media-source objects on a per-track attachment basis.
   If the same track is attached multiple times this results in
   multiple media-source objects, but the spec says it should be on a
   per-source basis.
2. framesPerSecond is only calculated after connecting (when we have a
   sender with SSRC), but if collected on a per-source basis the source
   should be able to tell us the FPS whether or not we are sending it.

Bug: webrtc:10453
Change-Id: I23705a79f15075dca2536275934af1904a7f0d39
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/137804
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28028}

stats/rtcstats_objects.cc

@@ -361,6 +361,7 @@ RTCMediaStreamStats::~RTCMediaStreamStats() {}
 // clang-format off
 WEBRTC_RTCSTATS_IMPL(RTCMediaStreamTrackStats, RTCStats, "track",
                      &track_identifier,
+                     &media_source_id,
                      &remote_source,
                      &ended,
                      &detached,
@@ -409,6 +410,7 @@ RTCMediaStreamTrackStats::RTCMediaStreamTrackStats(std::string&& id,
                                                    const char* kind)
     : RTCStats(std::move(id), timestamp_us),
       track_identifier("trackIdentifier"),
+      media_source_id("mediaSourceId"),
       remote_source("remoteSource"),
       ended("ended"),
       detached("detached"),
@@ -463,6 +465,7 @@ RTCMediaStreamTrackStats::RTCMediaStreamTrackStats(
     const RTCMediaStreamTrackStats& other)
     : RTCStats(other.id(), other.timestamp_us()),
       track_identifier(other.track_identifier),
+      media_source_id(other.media_source_id),
       remote_source(other.remote_source),
       ended(other.ended),
       detached(other.detached),
@@ -668,6 +671,7 @@ RTCInboundRTPStreamStats::~RTCInboundRTPStreamStats() {}
 // clang-format off
 WEBRTC_RTCSTATS_IMPL(
     RTCOutboundRTPStreamStats, RTCRTPStreamStats, "outbound-rtp",
+    &media_source_id,
     &packets_sent,
     &retransmitted_packets_sent,
     &bytes_sent,
@@ -687,6 +691,7 @@ RTCOutboundRTPStreamStats::RTCOutboundRTPStreamStats(const std::string& id,
 RTCOutboundRTPStreamStats::RTCOutboundRTPStreamStats(std::string&& id,
                                                      int64_t timestamp_us)
     : RTCRTPStreamStats(std::move(id), timestamp_us),
+      media_source_id("mediaSourceId"),
       packets_sent("packetsSent"),
       retransmitted_packets_sent("retransmittedPacketsSent"),
       bytes_sent("bytesSent"),
@@ -701,6 +706,7 @@ RTCOutboundRTPStreamStats::RTCOutboundRTPStreamStats(std::string&& id,
 RTCOutboundRTPStreamStats::RTCOutboundRTPStreamStats(
     const RTCOutboundRTPStreamStats& other)
     : RTCRTPStreamStats(other),
+      media_source_id(other.media_source_id),
       packets_sent(other.packets_sent),
       retransmitted_packets_sent(other.retransmitted_packets_sent),
       bytes_sent(other.bytes_sent),
@@ -714,6 +720,73 @@ RTCOutboundRTPStreamStats::RTCOutboundRTPStreamStats(
 
 RTCOutboundRTPStreamStats::~RTCOutboundRTPStreamStats() {}
 
+// clang-format off
+WEBRTC_RTCSTATS_IMPL(RTCMediaSourceStats, RTCStats, "parent-media-source",
+    &track_identifier,
+    &kind)
+// clang-format on
+
+RTCMediaSourceStats::RTCMediaSourceStats(const std::string& id,
+                                         int64_t timestamp_us)
+    : RTCMediaSourceStats(std::string(id), timestamp_us) {}
+
+RTCMediaSourceStats::RTCMediaSourceStats(std::string&& id, int64_t timestamp_us)
+    : RTCStats(std::move(id), timestamp_us),
+      track_identifier("trackIdentifier"),
+      kind("kind") {}
+
+RTCMediaSourceStats::RTCMediaSourceStats(const RTCMediaSourceStats& other)
+    : RTCStats(other.id(), other.timestamp_us()),
+      track_identifier(other.track_identifier),
+      kind(other.kind) {}
+
+RTCMediaSourceStats::~RTCMediaSourceStats() {}
+
+// clang-format off
+WEBRTC_RTCSTATS_IMPL_NO_MEMBERS(
+    RTCAudioSourceStats, RTCMediaSourceStats, "media-source")
+// clang-format on
+
+RTCAudioSourceStats::RTCAudioSourceStats(const std::string& id,
+                                         int64_t timestamp_us)
+    : RTCAudioSourceStats(std::string(id), timestamp_us) {}
+
+RTCAudioSourceStats::RTCAudioSourceStats(std::string&& id, int64_t timestamp_us)
+    : RTCMediaSourceStats(std::move(id), timestamp_us) {}
+
+RTCAudioSourceStats::RTCAudioSourceStats(const RTCAudioSourceStats& other)
+    : RTCMediaSourceStats(other) {}
+
+RTCAudioSourceStats::~RTCAudioSourceStats() {}
+
+// clang-format off
+WEBRTC_RTCSTATS_IMPL(RTCVideoSourceStats, RTCMediaSourceStats, "media-source",
+    &width,
+    &height,
+    &frames,
+    &frames_per_second)
+// clang-format on
+
+RTCVideoSourceStats::RTCVideoSourceStats(const std::string& id,
+                                         int64_t timestamp_us)
+    : RTCVideoSourceStats(std::string(id), timestamp_us) {}
+
+RTCVideoSourceStats::RTCVideoSourceStats(std::string&& id, int64_t timestamp_us)
+    : RTCMediaSourceStats(std::move(id), timestamp_us),
+      width("width"),
+      height("height"),
+      frames("frames"),
+      frames_per_second("framesPerSecond") {}
+
+RTCVideoSourceStats::RTCVideoSourceStats(const RTCVideoSourceStats& other)
+    : RTCMediaSourceStats(other),
+      width(other.width),
+      height(other.height),
+      frames(other.frames),
+      frames_per_second(other.frames_per_second) {}
+
+RTCVideoSourceStats::~RTCVideoSourceStats() {}
+
 // clang-format off
 WEBRTC_RTCSTATS_IMPL(RTCTransportStats, RTCStats, "transport",
     &bytes_sent,