Add support for tracking loading behavior of child frames.

chrome/browser/page_load_metrics/metrics_web_contents_observer.cc

Index: chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
diff --git a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
index ba63fd9f6e830ed1cfb9d68dbd1a4b91c6e8bf65..8117d1f70fe688612b0366e99f57da94c304630b 100644
--- a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
+++ b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
@@ -510,9 +510,14 @@ void MetricsWebContentsObserver::OnTimingUpdated(
     content::RenderFrameHost* render_frame_host,
     const PageLoadTiming& timing,
     const PageLoadMetadata& metadata) {
+  content::RenderFrameHost* root_render_frame_host = render_frame_host;

[Charlie Harrison, 2017/03/08 21:47:17]

I would probably prefer GetRenderViewHost()->GetMainFrame() so you don't have to
walk the frame tree.

[Bryan McQuade, 2017/03/09 03:06:11]

ah, absolutely, thanks! didn't know about that.

+  while (root_render_frame_host->GetParent() != nullptr) {
+    root_render_frame_host = root_render_frame_host->GetParent();
+  }
+
   // We may receive notifications from frames that have been navigated away
   // from. We simply ignore them.
-  if (render_frame_host != web_contents()->GetMainFrame()) {
+  if (root_render_frame_host != web_contents()->GetMainFrame()) {
     RecordInternalError(ERR_IPC_FROM_WRONG_FRAME);
     return;
   }
@@ -535,6 +540,15 @@ void MetricsWebContentsObserver::OnTimingUpdated(
   if (error)
     return;
 
+  if (render_frame_host->GetParent() != nullptr) {
+    // Child frames may send PageLoadMetadata updates, but not PageLoadTiming
+    // updates.
+    if (!timing.IsEmpty())
+      RecordInternalError(ERR_TIMING_IPC_FROM_SUBFRAME);
+    committed_load_->UpdateChildMetadata(metadata);
+    return;
+  }
+
   if (!committed_load_->UpdateTiming(timing, metadata)) {
     // If the page load tracker cannot update its timing, something is wrong
     // with the IPC (it's from another load, or it's invalid in some other way).