peerconnection: measure bundle policy usage

measured in the connectionstatechange event to connected which usually
happens once per connection.

BUG=webrtc:12383

Change-Id: Ida136c44bfe65e922627390747f8bee384603715
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/204301
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Justin Uberti <juberti@webrtc.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/master@{#33207}

api/uma_metrics.h

@@ -191,6 +191,17 @@ enum BundleUsage {
   kBundleUsageMax
 };
 
+// Metrics for reporting configured BUNDLE policy, mapping directly to
+// https://w3c.github.io/webrtc-pc/#rtcbundlepolicy-enum
+// These values are persisted to logs. Entries should not be renumbered and
+// numeric values should never be reused.
+enum BundlePolicyUsage {
+  kBundlePolicyUsageBalanced = 0,
+  kBundlePolicyUsageMaxBundle = 1,
+  kBundlePolicyUsageMaxCompat = 2,
+  kBundlePolicyUsageMax
+};
+
 // When adding new metrics please consider using the style described in
 // https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/README.md#usage
 // instead of the legacy enums used above.

pc/peer_connection.cc

@@ -1738,6 +1738,27 @@ void PeerConnection::SetConnectionState(
     return;
   connection_state_ = new_state;
   Observer()->OnConnectionChange(new_state);
+
+  // The connection state change to connected usually happens once per
+  // connection which makes it a good point to report metrics.
+  if (new_state == PeerConnectionState::kConnected) {
+    // Record bundle-policy from configuration. Done here from
+    // connectionStateChange to limit to actually established connections.
+    BundlePolicyUsage policy = kBundlePolicyUsageMax;
+    switch (configuration_.bundle_policy) {
+      case kBundlePolicyBalanced:
+        policy = kBundlePolicyUsageBalanced;
+        break;
+      case kBundlePolicyMaxBundle:
+        policy = kBundlePolicyUsageMaxBundle;
+        break;
+      case kBundlePolicyMaxCompat:
+        policy = kBundlePolicyUsageMaxCompat;
+        break;
+    }
+    RTC_HISTOGRAM_ENUMERATION("WebRTC.PeerConnection.BundlePolicy", policy,
+                              kBundlePolicyUsageMax);
+  }
 }
 
 void PeerConnection::OnIceGatheringChange(