[DOMSize] Filter by pid on cross-origin navigations

DOM stats events can leak across cross-origin navigations because
the pages before and after the navigation will not share a process.

This CL prevents DOM stats from leaking by also checking for the
correct PID for insights related to a navigation.

Bug: None
Change-Id: I1df8e8451bcefbf6807a6e2d32cb22630ddf7505
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6219828
Commit-Queue: Paul Irish <[email protected]>
Auto-Submit: Adam Raine <[email protected]>
Reviewed-by: Paul Irish <[email protected]>

Author: Adam Raine

front_end/models/trace/insights/DOMSize.test.ts

@@ -41,4 +41,23 @@ describeWithEnvironment('DOMSize', function() {
     assert.strictEqual(domStats.maxChildren!.numChildren, 4);
     assert.strictEqual(domStats.maxChildren!.nodeName, 'BODY');
   });
+
+  it('separates dom stats in a cross-origin navigation', async () => {
+    const {data, insights} = await processTrace(this, 'dom-size-overlap.json.gz');
+
+    const navigations =
+        [...data.Meta.navigationsByNavigationId.values()].filter(n => n.args.data?.isOutermostMainFrame);
+    {
+      const insight = getInsightOrError('DOMSize', insights, navigations[0]);
+      const domStats = insight.maxDOMStats!.args.data;
+      assert.strictEqual(domStats.totalElements, 6811);
+    }
+    {
+      const insight = getInsightOrError('DOMSize', insights, navigations[1]);
+      const domStats = insight.maxDOMStats!.args.data;
+      // If we don't filter by process id, the DOM stats events from the previous navigation
+      // would leak into this one and this # would be much higher
+      assert.strictEqual(domStats.totalElements, 7);
+    }
+  });
 });

front_end/models/trace/insights/DOMSize.ts

@@ -124,6 +124,14 @@ export function generateInsight(
   const domStatsEvents = parsedTrace.DOMStats.domStatsByFrameId.get(context.frameId)?.filter(isWithinContext) ?? [];
   let maxDOMStats: Types.Events.DOMStats|undefined;
   for (const domStats of domStatsEvents) {
+    // While recording a cross-origin navigation, there can be overlapping dom stats from before & after
+    // the navigation which share a frameId. In this case we should also ensure the pid matches up with
+    // the navigation we care about (i.e. from after the navigation event).
+    const navigationPid = context.navigation?.pid;
+    if (navigationPid && domStats.pid !== navigationPid) {
+      continue;
+    }
+
     if (!maxDOMStats || domStats.args.data.totalElements > maxDOMStats.args.data.totalElements) {
       maxDOMStats = domStats;
     }

front_end/panels/timeline/fixtures/traces/BUILD.gn

@@ -22,6 +22,7 @@ copy_to_gen("traces") {
     "cls-single-frame.json.gz",
     "crux.json.gz",
     "dom-size-long.json.gz",
+    "dom-size-overlap.json.gz",
     "dom-size.json.gz",
     "enhanced-traces.json.gz",
     "extension-tracks-and-marks.json.gz",

front_end/panels/timeline/fixtures/traces/README.md

@@ -250,3 +250,7 @@ This is a trace where a `LargestImagePaint` event occurs after the last `largest
 ### web-dev-screenshot-source-ids
 
 A trace generated from crrev.com/c/6197645 (January 2025), which changed the format of screenshots from the legacy OBJECT_SNAPSHOT format to be instant events with more information attached to them.
+
+### dom-size-overlap
+
+Trace containing a cross-origin navigation where DOM size events from the pre-navigation page are emitted *after* the navigation event.