perf_hooks,http2: add clearHttp2 to remove http2 entries

Add missing clearHttp2 method to `perf_hooks.performance` to
remove the http2 entries from the master timeline to prevent
that from being a memory leak.

Author: jasnell

doc/api/perf_hooks.md

@@ -39,6 +39,13 @@ added: v8.5.0
 If `name` is not provided, removes all `PerformanceFunction` objects from the
 Performance Timeline. If `name` is provided, removes entries with `name`.
 
+### performance.clearHttp2()
+<!-- YAML
+added: REPLACEME
+-->
+
+Remove all `http2` performance entry objects from the Performance Timeline.
+
 ### performance.clearMarks([name])
 <!-- YAML
 added: v8.5.0

lib/perf_hooks.js

@@ -471,6 +471,10 @@ class Performance extends PerformanceObserverEntryList {
     this[kClearEntry]('function', name);
   }
 
+  clearHttp2() {
+    this[kClearEntry]('http2');
+  }
+
   timerify(fn) {
     if (typeof fn !== 'function') {
       const errors = lazyErrors();

test/parallel/test-http2-perf_hooks.js

@@ -6,7 +6,7 @@ if (!common.hasCrypto)
 const assert = require('assert');
 const h2 = require('http2');
 
-const { PerformanceObserver } = require('perf_hooks');
+const { PerformanceObserver, performance } = require('perf_hooks');
 
 const obs = new PerformanceObserver(common.mustCall((items) => {
   const entry = items.getEntries()[0];
@@ -46,6 +46,7 @@ const obs = new PerformanceObserver(common.mustCall((items) => {
     default:
       assert.fail('invalid entry name');
   }
+  performance.clearHttp2();
 }, 4));
 obs.observe({ entryTypes: ['http2'] });
 
@@ -100,3 +101,8 @@ server.on('listening', common.mustCall(() => {
   }));
 
 }));
+
+process.on('exit', () => {
+  // There shouldn't be any http2 entries left over.
+  assert.strictEqual(performance.getEntries().length, 1);
+});