core(uses-http2): include multiplexable assets when 1p is a known 3p origin

core/audits/dobetterweb/uses-http2.js

@@ -152,16 +152,19 @@
    * @param {LH.Artifacts.EntityClassification} classifiedEntities
    * @return {boolean}
    */
-  static isStaticAsset(networkRequest, classifiedEntities) {
+  static isMultiplexableStaticAsset(networkRequest, classifiedEntities) {
     if (!STATIC_RESOURCE_TYPES.has(networkRequest.resourceType)) return false;
 
     // Resources from third-parties that are less than 100 bytes are usually tracking pixels, not actual resources.
     // They can masquerade as static types though (gifs, documents, etc)
     if (networkRequest.resourceSize < 100) {
-      // This logic needs to be revisited.
-      // See https://github.com/GoogleChrome/lighthouse/issues/14661
       const entity = classifiedEntities.entityByUrl.get(networkRequest.url);
-      if (entity && !entity.isUnrecognized) return false;
+      if (entity) {
+        // Third-party assets are multiplexable in their first-party context.
+        if (classifiedEntities.firstParty?.name === entity.name) return true;
+        // Skip recognizable third-parties' requests.
+        if (!entity.isUnrecognized) return false;
+      }
     }
 
     return true;
@@ -199,7 +202,7 @@
     /** @type {Map<string, Array<LH.Artifacts.NetworkRequest>>} */
     const groupedByOrigin = new Map();
     for (const record of networkRecords) {
-      if (!UsesHTTP2Audit.isStaticAsset(record, classifiedEntities)) continue;
+      if (!UsesHTTP2Audit.isMultiplexableStaticAsset(record, classifiedEntities)) continue;
       if (UrlUtils.isLikeLocalhost(record.parsedURL.host)) continue;
       const existing = groupedByOrigin.get(record.parsedURL.securityOrigin) || [];
       existing.push(record);

core/test/audits/dobetterweb/uses-http2-test.js

@@ -265,4 +265,58 @@ describe('Resources are fetched over http/2', () => {
     expect(result.score).toEqual(0);
     expect(result.metricSavings).toBeUndefined();
   });
+
+  it('should identify multiplexable assets when run on recognizable 3p origins', async () => {
+    const networkRecords = [
+      {
+        url: 'https://www.twitter.com/',
+        priority: 'High',
+        protocol: 'HTTP/1.1',
+      },
+      {
+        url: 'https://www.twitter.com/2',
+        priority: 'High',
+        protocol: 'HTTP/1.1',
+      },
+      {
+        url: 'https://www.twitter.com/3',
+        priority: 'High',
+        protocol: 'HTTP/1.1',
+      },
+      {
+        url: 'https://www.twitter.com/4',
+        priority: 'High',
+        protocol: 'HTTP/1.1',
+      },
+      {
+        url: 'https://www.twitter.com/5',
+        priority: 'High',
+        protocol: 'HTTP/1.1',
+      },
+      {
+        url: 'https://www.twitter.com/embed/foo',
+        priority: 'High',
+        protocol: 'HTTP/1.1',
+      },
+      {
+        url: 'https://www.facebook.com/embed',
+        protocol: 'HTTP/1.1',
+        priority: 'High',
+      },
+    ];
+    const artifacts = buildArtifacts(networkRecords);
+    artifacts.devtoolsLogs.defaultPass = networkRecordsToDevtoolsLog(networkRecords);
+
+    const result = await UsesHTTP2Audit.audit(artifacts, context);
+    const urls = new Set(result.details.items.map(item => item.url));
+    const hosts = new Set(result.details.items.map(item => new URL(item.url).host));
+
+    // Make sure we don't pull in actual 3p domains.
+    expect(hosts).toEqual(new Set(['www.twitter.com']));
+
+    // Make sure we dont flag the 3rd party request for multiplexing.
+    expect(urls).not.toContain('https://www.facebook.com/embed');
+
+    expect(result.details.items).toHaveLength(6);
+  });
 });