PageLoadMetrics renderer and browser implementation.

chrome/renderer/chrome_content_renderer_client.cc

Index: chrome/renderer/chrome_content_renderer_client.cc
diff --git a/chrome/renderer/chrome_content_renderer_client.cc b/chrome/renderer/chrome_content_renderer_client.cc
index 5e43723656075bbd6285940079f8063b398a8082..cd7e930b005358b83307b45c38cd9806749b0418 100644
--- a/chrome/renderer/chrome_content_renderer_client.cc
+++ b/chrome/renderer/chrome_content_renderer_client.cc
@@ -64,6 +64,7 @@
 #include "components/nacl/renderer/ppb_nacl_private.h"
 #include "components/nacl/renderer/ppb_nacl_private_impl.h"
 #include "components/network_hints/renderer/prescient_networking_dispatcher.h"
+#include "components/page_load_metrics/renderer/metrics_render_frame_observer.h"
 #include "components/password_manager/content/renderer/credential_manager_client.h"
 #include "components/pdf/renderer/pepper_pdf_host.h"
 #include "components/plugins/renderer/mobile_youtube_plugin.h"
@@ -570,6 +571,12 @@ void ChromeContentRendererClient::RenderFrameCreated(
   new dom_distiller::DistillerJsRenderFrameObserver(
       render_frame, chrome::ISOLATED_WORLD_ID_CHROME_INTERNAL);
 
+  if (render_frame->GetWebFrame()->parent() == nullptr) {
+    // Only attach MainRenderFrameObserver to the main frame, since
+    // we only want to log page load metrics for the main frame.
+    new page_load_metrics::MetricsRenderFrameObserver(render_frame);
+  }
+
   PasswordAutofillAgent* password_autofill_agent =
       new PasswordAutofillAgent(render_frame);
   PasswordGenerationAgent* password_generation_agent =