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..f558c754579a2541c2261ec47c6c89ffebf70c8c 100644
--- a/content/browser/loader/navigation_url_loader_delegate.h
+++ b/content/browser/loader/navigation_url_loader_delegate.h
@@ -39,6 +39,12 @@ class CONTENT_EXPORT NavigationURLLoaderDelegate {
   // network error code for the failure.
   virtual void OnRequestFailed(int net_error) = 0;
 
+  // Called after the network request has begun on the IO thread at time
+  // |timestamp|. This is just a thread hop but is used to compare timing
+  // against the pre-PlzNavigate codepath which didn't start the network request
+  // until after the renderer was initialized.
+  virtual void OnRequestStarted(base::TimeTicks timestamp) = 0;
+
  protected:
   NavigationURLLoaderDelegate() {}
   virtual ~NavigationURLLoaderDelegate() {}