Instrument RTCIceCandidate attributes for Identifiability study.

Instrument RTCIceCandidate.{address,candidate,port,relatedAddress,relatedPort} for web Identifiability study.

Bug: 973801
Change-Id: If0783bc203c996cf7603b47395e1f628905ac9f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2359735
Commit-Queue: Russ Hamilton <behamilton@google.com>
Reviewed-by: Florent Castelli <orphis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800313}

third_party/blink/public/mojom/web_feature/web_feature.mojom

@@ -2763,6 +2763,11 @@ enum WebFeature {
   kGamepadId = 3434,
   kElementAttachInternals = 3435,
   kBluetoothDeviceName = 3436,
+  kRTCIceCandidateAddress = 3437,
+  kRTCIceCandidateCandidate = 3438,
+  kRTCIceCandidatePort = 3439,
+  kRTCIceCandidateRelatedAddress = 3440,
+  kRTCIceCandidateRelatedPort = 3441,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.

third_party/blink/renderer/modules/peerconnection/rtc_ice_candidate.idl

@@ -60,19 +60,19 @@ enum RTCIceTcpCandidateType {
     Exposed=Window
 ] interface RTCIceCandidate {
     [CallWith=ExecutionContext, RaisesException] constructor(optional RTCIceCandidateInit candidateInitDict = {});
-    readonly attribute DOMString candidate;
+    [HighEntropy=Direct, MeasureAs=RTCIceCandidateCandidate] readonly attribute DOMString candidate;
     readonly attribute DOMString? sdpMid;
     readonly attribute unsigned short? sdpMLineIndex;
     readonly attribute DOMString? foundation;
     readonly attribute RTCIceComponent? component;
     readonly attribute unsigned long? priority;
-    readonly attribute DOMString? address;
+    [HighEntropy=Direct, MeasureAs=RTCIceCandidateAddress] readonly attribute DOMString? address;
     readonly attribute RTCIceProtocol? protocol;
-    readonly attribute unsigned short? port;
+    [HighEntropy=Direct, MeasureAs=RTCIceCandidatePort] readonly attribute unsigned short? port;
     readonly attribute RTCIceCandidateType? type;
     readonly attribute RTCIceTcpCandidateType? tcpType;
-    readonly attribute DOMString? relatedAddress;
-    readonly attribute unsigned short? relatedPort;
+    [HighEntropy=Direct, MeasureAs=RTCIceCandidateRelatedAddress] readonly attribute DOMString? relatedAddress;
+    [HighEntropy=Direct, MeasureAs=RTCIceCandidateRelatedPort] readonly attribute unsigned short? relatedPort;
     readonly attribute DOMString? usernameFragment;
     // TODO(peria): Return type should be RTCIceCandidateInit.
     [CallWith=ScriptState, ImplementedAs=toJSONForBinding] object toJSON();

tools/metrics/histograms/enums.xml

@@ -28868,6 +28868,11 @@ Called by update_use_counter_feature_enum.py.-->
   <int value="3434" label="GamepadId"/>
   <int value="3435" label="ElementAttachInternals"/>
   <int value="3436" label="BluetoothDeviceName"/>
+  <int value="3437" label="RTCIceCandidateAddress"/>
+  <int value="3438" label="RTCIceCandidateCandidate"/>
+  <int value="3439" label="RTCIceCandidatePort"/>
+  <int value="3440" label="RTCIceCandidateRelatedAddress"/>
+  <int value="3441" label="RTCIceCandidateRelatedPort"/>
 </enum>
 
 <enum name="FeaturePolicyAllowlistType">