New TimeToFirstURLJob* navigation metrics now work with PlzNavigate.

content/browser/loader/navigation_url_loader_impl.h

Index: content/browser/loader/navigation_url_loader_impl.h
diff --git a/content/browser/loader/navigation_url_loader_impl.h b/content/browser/loader/navigation_url_loader_impl.h
index ecfd2382e8e9d3b33a7f1161795f3535b2489aae..7dba11851ff2fda4abf9a42ab877ae172e120915 100644
--- a/content/browser/loader/navigation_url_loader_impl.h
+++ b/content/browser/loader/navigation_url_loader_impl.h
@@ -9,6 +9,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/time/time.h"
 #include "content/browser/loader/navigation_url_loader.h"
 
 namespace net {
@@ -50,6 +51,10 @@ class NavigationURLLoaderImpl : public NavigationURLLoader {
   // Notifies the delegate the request failed to return a response.
   void NotifyRequestFailed(int net_error);
 
+  // Notifies the delegate the begin navigation request was handled and a
+  // potential first network request is about to be made.
+  void NotifyRequestStarted(base::TimeTicks timestamp);
+
   NavigationURLLoaderDelegate* delegate_;
 
   // |core_| is deleted on the IO thread in a subsequent task when the