New TimeToFirstURLJob* navigation metrics now work with PlzNavigate.

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index 332b7ec84a98ee2d3eb9ef55ad006f4b1594e59f..f829176e35c9dec74a89598d845f4bb9ab33a511 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -978,7 +978,9 @@ void ResourceDispatcherHostImpl::OnRequestResource(
     const ResourceHostMsg_Request& request_data) {
   // When logging time-to-network only care about main frame and non-transfer
   // navigations.
-  if (request_data.resource_type == RESOURCE_TYPE_MAIN_FRAME &&
+  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableBrowserSideNavigation) &&
+      request_data.resource_type == RESOURCE_TYPE_MAIN_FRAME &&
       request_data.transferred_request_request_id == -1) {
     BrowserThread::PostTask(
         BrowserThread::UI,
@@ -2007,6 +2009,9 @@ void ResourceDispatcherHostImpl::BeginNavigationRequest(
                                 -1,  // route_id
                                 handler.Pass());
 
+  if (info.is_main_frame)
+    loader->AboutToBeginNavigation(TimeTicks::Now());
+
   BeginRequestInternal(new_request.Pass(), handler.Pass());
 }