New TimeToFirstURLJob* navigation metrics now work with PlzNavigate.

content/browser/frame_host/navigator.h

Index: content/browser/frame_host/navigator.h
diff --git a/content/browser/frame_host/navigator.h b/content/browser/frame_host/navigator.h
index 191a58366227634b7e51db019cc8cdf6f5453019..2b81bc17c5733784279643a276b0821bbba8e0b7 100644
--- a/content/browser/frame_host/navigator.h
+++ b/content/browser/frame_host/navigator.h
@@ -143,6 +143,12 @@ class CONTENT_EXPORT Navigator : public base::RefCounted<Navigator> {
   virtual void LogResourceRequestTime(
     base::TimeTicks timestamp, const GURL& url) {};
 
+  // PlzNavigate
+  // Called when ResourceDispacherHostImpl is about to begin working on a

[clamy, 2015/01/27 12:35:04]

s/is about to begin working/has started working

[carlosk, 2015/01/27 17:12:03]

Done.

+  // navigation request, right before the first network request is made so that
+  // the timestamp can be recorded into an histogram.
+  virtual void LogAboutToBeginNavigation(base::TimeTicks timestamp) {};

[carlosk, 2015/01/26 19:54:01]

I switched the method name here, adding the Log prefix because for Navigator the
logging is the purpose of this call.

For the whole loader hierarchy what matters is the more generic notification
that the navigation is about to begin, hence it not having the same prefix.

[clamy, 2015/01/27 12:35:03]

Acknowledged.

+
   // Called to record the time it took to execute the before unload hook for the
   // current navigation.
   virtual void LogBeforeUnloadTime(