Collecting RTCIceCandidatePairStats.transport_id and improved unittests

webrtc/stats/rtcstats.cc

Index: webrtc/stats/rtcstats.cc
diff --git a/webrtc/stats/rtcstats.cc b/webrtc/stats/rtcstats.cc
index ef3666605689b0d04ca7adc182f8b993760740a6..1968dd030e0fbc7b5f3300837f2ec880f538659a 100644
--- a/webrtc/stats/rtcstats.cc
+++ b/webrtc/stats/rtcstats.cc
@@ -51,10 +51,8 @@ std::string VectorOfStringsToString(const std::vector<T>& strings) {
 }  // namespace
 
 bool RTCStats::operator==(const RTCStats& other) const {
-  if (type() != other.type() || id() != other.id() ||
-      timestamp_us() != other.timestamp_us()) {
+  if (type() != other.type() || id() != other.id())
     return false;
-  }
   std::vector<const RTCStatsMemberInterface*> members = Members();
   std::vector<const RTCStatsMemberInterface*> other_members = other.Members();
   RTC_DCHECK_EQ(members.size(), other_members.size());