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..14c3a44b2f740dd48501d50502ba6cb3c776311f 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 NotifyRequestHandled(base::TimeTicks timestamp);

[davidben, 2015/02/03 23:54:40]

Nit: I would prefer "OnRequestStart" or "OnRequestStarted" or maybe
"OnRequestReady" rather than "OnRequestHandled". "Handled" to me says that the
network request is done. ("I have handled the request and can move on to
something else.)

But this name has changed plenty enough so I'm not going to re-open the debate
if everyone else is happy with the name. :-)

[carlosk, 2015/02/04 10:21:32]

Given this and nasko@'s reply I'll change the names to [On|Notify]RequestStarted
depending on the prefix already in use in changed class.

+
   NavigationURLLoaderDelegate* delegate_;
 
   // |core_| is deleted on the IO thread in a subsequent task when the