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..dd1358eecc40605ebb1f65b8c07c3c7ebb68a780 100644
--- a/content/browser/frame_host/navigator.h
+++ b/content/browser/frame_host/navigator.h
@@ -140,6 +140,11 @@ class CONTENT_EXPORT Navigator : public base::RefCounted<Navigator> {
 
   // Called when the first resource request for a given navigation is executed
   // so that it can be tracked into an histogram.
+  // PlzNavigate: Called when a navigation is about to make its first potential

[nasko, 2015/02/02 18:28:53]

nit: Why is it "potential"? Don't we always make a request for a navigation?

[carlosk, 2015/02/03 11:00:04]

So I just learned about that as well from clamy@: it is potential because before
the network is touched there is a cache check that if successful might
completely avoid the network.

[clamy, 2015/02/03 12:13:54]

Maybe we can rephrase that as Called when the network stack started handling the
navigation request (since this is what we care about, and not whether we end
serving the request from cache or the network).

[carlosk, 2015/02/03 12:48:34]

Done.

+  // network request so that the timestamp can be recorded into an histogram.
+  // TODO(carlosk): once PlzNavigate is the only navigation implementation
+  // remove the URL parameter and rename this method to better suit its naming
+  // conventions.
   virtual void LogResourceRequestTime(
     base::TimeTicks timestamp, const GURL& url) {};