New TimeToFirstURLJob* navigation metrics now work with PlzNavigate.

content/browser/loader/navigation_url_loader_delegate.h

Index: content/browser/loader/navigation_url_loader_delegate.h
diff --git a/content/browser/loader/navigation_url_loader_delegate.h b/content/browser/loader/navigation_url_loader_delegate.h
index 199f48a2a984b238f4f2f0f49f287bcc88352a9f..248842ef945ce88a37bdda7917fc9b7a3415dace 100644
--- a/content/browser/loader/navigation_url_loader_delegate.h
+++ b/content/browser/loader/navigation_url_loader_delegate.h
@@ -39,6 +39,11 @@ class CONTENT_EXPORT NavigationURLLoaderDelegate {
   // network error code for the failure.
   virtual void OnRequestFailed(int net_error) = 0;
 
+  // Called when a begin navigation request is handled, right before the

[davidben, 2015/02/02 22:33:57]

"Called when a begin navigation request is handled" seems a little weird.

[davidben, 2015/02/02 22:37:06]

Sorry, never finished this comment.

Perhaps:
// Called after the network request has begun on the IO thread at time
|timestamp|. This is just a thread hop but is to compare timing against the
pre-PlzNavigate codepath which didn't start the network request until after the
renderer was initialized.

[carlosk, 2015/02/03 11:00:04]

Done.

+  // first potential network request happens, providing the |timestamp| when
+  // that happened in the IO thread.
+  virtual void NavigationRequested(base::TimeTicks timestamp) = 0;

[nasko, 2015/02/02 18:28:53]

nit: OnNavigationRequested? mainly to match the naming pattern of the methods
above.

[carlosk, 2015/02/03 11:00:04]

Done.

+
  protected:
   NavigationURLLoaderDelegate() {}
   virtual ~NavigationURLLoaderDelegate() {}