Send an event to the page load metrics to track resource starting.

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 a58984656eec1b8effd05e16e67ee570f0d744ab..242eece6415103c18128322c10e64f9a510928c3 100644
--- a/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
+++ b/chrome/browser/page_load_metrics/metrics_web_contents_observer.cc
@@ -252,6 +252,18 @@ PageLoadTracker* MetricsWebContentsObserver::GetTrackerOrNullForRequest(
   return nullptr;
 }
 
+void MetricsWebContentsObserver::OnRequestStarted(
+    const content::GlobalRequestID& request_id,
+    content::ResourceType resource_type,
+    base::TimeTicks creation_time) {
+  PageLoadTracker* tracker =
+      GetTrackerOrNullForRequest(request_id, resource_type, creation_time);

[RyanSturm, 2017/04/14 20:08:43]

As a note, Ibelieve this won't properly track the main page request as there
won't be a corresponding PageLoadTracker yet. This might be fixed if
GlobalRequestID is set in an earlier callback.

Please add comments about main page requests (can you verify that they are not
tracked properly).

[Pete Williamson, 2017/04/17 18:53:11]

Comment added.  We aren't tracking the main page today, so it should be fine as
is.

+  if (tracker) {
+    ExtraRequestStartInfo extra_request_start_info(resource_type);
+    tracker->OnStartedResource(extra_request_start_info);
+  }
+}
+
 void MetricsWebContentsObserver::OnRequestComplete(
     const content::GlobalRequestID& request_id,
     content::ResourceType resource_type,
@@ -263,10 +275,10 @@ void MetricsWebContentsObserver::OnRequestComplete(
   PageLoadTracker* tracker =
       GetTrackerOrNullForRequest(request_id, resource_type, creation_time);
   if (tracker) {
-    ExtraRequestInfo extra_request_info(
+    ExtraRequestCompleteInfo extra_request_complete_info(
         was_cached, raw_body_bytes, used_data_reduction_proxy,
-        was_cached ? 0 : original_content_length);
-    tracker->OnLoadedResource(extra_request_info);
+        was_cached ? 0 : original_content_length, resource_type);
+    tracker->OnLoadedResource(extra_request_complete_info);
   }
 }