Add missing method definition for StatsReport::Value::id_val()

Also add a preprocessor definition to avoid redefinition in downstream projects.

Bug: webrtc:15241
Change-Id: Ic55d98c3d3a69b9b19195ee78f03af6e38fdd0e2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/308601
Reviewed-by: Harald Alvestrand <[email protected]>
Reviewed-by: Henrik Boström <[email protected]>
Reviewed-by: Jonas Oreland <[email protected]>
Commit-Queue: Sameer Vijaykar <[email protected]>
Cr-Commit-Position: refs/heads/main@{#40289}

Author: sam-vi

api/legacy_stats_types.cc

@@ -362,6 +362,11 @@ bool StatsReport::Value::bool_val() const {
   return value_.bool_;
 }
 
+const StatsReport::Id& StatsReport::Value::id_val() const {
+  RTC_DCHECK_EQ(type_, kId);
+  return *value_.id_;
+}
+
 const char* StatsReport::Value::display_name() const {
   switch (name) {
     case kStatsValueNameAecDivergentFilterFraction:

api/legacy_stats_types.h

@@ -333,6 +333,12 @@ class RTC_EXPORT StatsReport {
     bool bool_val() const;
     const Id& id_val() const;
 
+// TODO(bugs.webrtc.org/15241): remove this definition once downstream
+// definitions of StatsReport::Value::id_val() have been deleted.
+#ifndef WEBRTC_DEFINES_STATSREPORT_VALUE_ID_VAL
+#define WEBRTC_DEFINES_STATSREPORT_VALUE_ID_VAL
+#endif  // WEBRTC_DEFINES_STATSREPORT_VALUE_ID_VAL
+
     // Returns the string representation of `name`.
     const char* display_name() const;