[Stats] Delete unused NonStandardGroupId.

NonStandardGroupId is no longer wired up to Chrome, but if we did want
to only expose certain metrics if a field trial was enabled then the
right place to do that would be in blink, where WebIDL lives.

This was only used prior to the WebRtcStatsReportIdl launch and
experiments haven't been active in several years so its dead code.

Blocked on:
- https://chromium-review.googlesource.com/c/chromium/src/+/4514754

Bug: webrtc:15162
Change-Id: Ia41a4d21d7e5f029ddb121183fbd69ae7f98fac4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/304720
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40132}

api/stats/rtc_stats.h

@@ -206,21 +206,6 @@ class RTC_EXPORT RTCStats {
     return parent_class::MembersOfThisObjectAndAncestors(0);                \
   }
 
-// Non-standard stats members can be exposed to the JavaScript API in Chrome
-// e.g. through origin trials. The group ID can be used by the blink layer to
-// determine if a stats member should be exposed or not. Multiple non-standard
-// stats members can share the same group ID so that they are exposed together.
-enum class NonStandardGroupId {
-  // Group ID used for testing purposes only.
-  kGroupIdForTesting,
-  // I2E:
-  // https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/hE2B1iItPDk
-  kRtcAudioJitterBufferMaxPackets,
-  // I2E:
-  // https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/YbhMyqLXXXo
-  kRtcStatsRelativePacketArrivalDelay,
-};
-
 // Certain stat members should only be exposed to the JavaScript API in
 // certain circumstances as to avoid passive fingerprinting.
 enum class StatExposureCriteria : uint8_t {
@@ -274,9 +259,6 @@ class RTCStatsMemberInterface {
   bool is_standardized() const {
     return exposure_criteria() != StatExposureCriteria::kNonStandard;
   }
-  // Non-standard stats members can have group IDs in order to be exposed in
-  // JavaScript through experiments. Standardized stats have no group IDs.
-  virtual std::vector<NonStandardGroupId> group_ids() const { return {}; }
   // The conditions for exposing the statistic to JavaScript. Stats with
   // criteria that is not kAlways has some restriction and should be filtered
   // in accordance to the spec.
@@ -512,22 +494,14 @@ class RTCNonStandardStatsMember
  public:
   explicit RTCNonStandardStatsMember(const char* name)
       : RTCRestrictedStatsBase(name) {}
-  RTCNonStandardStatsMember(const char* name,
-                            std::initializer_list<NonStandardGroupId> group_ids)
-      : RTCRestrictedStatsBase(name), group_ids_(group_ids) {}
   RTCNonStandardStatsMember(const char* name, const T& value)
       : RTCRestrictedStatsBase(name, value) {}
   RTCNonStandardStatsMember(const char* name, T&& value)
       : RTCRestrictedStatsBase(name, std::move(value)) {}
   RTCNonStandardStatsMember(const RTCNonStandardStatsMember<T>& other)
-      : RTCRestrictedStatsBase(other), group_ids_(other.group_ids_) {}
+      : RTCRestrictedStatsBase(other) {}
   RTCNonStandardStatsMember(RTCNonStandardStatsMember<T>&& other)
-      : RTCRestrictedStatsBase(std::move(other)),
-        group_ids_(std::move(other.group_ids_)) {}
-
-  std::vector<NonStandardGroupId> group_ids() const override {
-    return group_ids_;
-  }
+      : RTCRestrictedStatsBase(std::move(other)) {}
 
   T& operator=(const T& value) {
     return RTCRestrictedStatsMember<
@@ -541,7 +515,6 @@ class RTCNonStandardStatsMember
  private:
   using RTCRestrictedStatsBase =
       RTCRestrictedStatsMember<T, StatExposureCriteria::kNonStandard>;
-  std::vector<NonStandardGroupId> group_ids_;
 };
 
 extern template class RTC_EXPORT_TEMPLATE_DECLARE(RTC_EXPORT)

stats/rtc_stats_unittest.cc

@@ -518,16 +518,6 @@ TEST(RTCStatsTest, RestrictedStatsTest) {
       << "These can not be equal as they have different exposure criteria.";
 }
 
-TEST(RTCStatsTest, NonStandardGroupId) {
-  auto group_id = NonStandardGroupId::kGroupIdForTesting;
-  RTCNonStandardStatsMember<int32_t> with_group_id("stat", {group_id});
-  std::vector<NonStandardGroupId> expected_ids({group_id});
-  EXPECT_EQ(expected_ids, with_group_id.group_ids());
-
-  RTCNonStandardStatsMember<int32_t> without_group_id("stat");
-  EXPECT_TRUE(without_group_id.group_ids().empty());
-}
-
 // Death tests.
 // Disabled on Android because death tests misbehave on Android, see
 // base/test/gtest_util.h.

stats/rtcstats_objects.cc

@@ -481,16 +481,9 @@ RTCInboundRtpStreamStats::RTCInboundRtpStreamStats(std::string id,
       qp_sum("qpSum"),
       goog_timing_frame_info("googTimingFrameInfo"),
       power_efficient_decoder("powerEfficientDecoder"),
-      jitter_buffer_flushes(
-          "jitterBufferFlushes",
-          {NonStandardGroupId::kRtcAudioJitterBufferMaxPackets}),
-      delayed_packet_outage_samples(
-          "delayedPacketOutageSamples",
-          {NonStandardGroupId::kRtcAudioJitterBufferMaxPackets,
-           NonStandardGroupId::kRtcStatsRelativePacketArrivalDelay}),
-      relative_packet_arrival_delay(
-          "relativePacketArrivalDelay",
-          {NonStandardGroupId::kRtcStatsRelativePacketArrivalDelay}),
+      jitter_buffer_flushes("jitterBufferFlushes"),
+      delayed_packet_outage_samples("delayedPacketOutageSamples"),
+      relative_packet_arrival_delay("relativePacketArrivalDelay"),
       interruption_count("interruptionCount"),
       total_interruption_duration("totalInterruptionDuration"),
       min_playout_delay("minPlayoutDelay"),