New TimeToFirstURLJob* navigation metrics now work with PlzNavigate.

content/browser/frame_host/navigator.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_FRAME_HOST_NAVIGATOR_H_
 #define CONTENT_BROWSER_FRAME_HOST_NAVIGATOR_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
@@ skipping 122 matching lines @@
                                 ResourceResponse* response,
                                 scoped_ptr<StreamHandle> body);
 
   // PlzNavigate
   // Cancel a NavigationRequest for |frame_tree_node|. Called when
   // |frame_tree_node| is destroyed.
   virtual void CancelNavigation(FrameTreeNode* frame_tree_node) {}
 
   // 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) {};
 
   // Called to record the time it took to execute the before unload hook for the
   // current navigation.
   virtual void LogBeforeUnloadTime(
       const base::TimeTicks& renderer_before_unload_start_time,
       const base::TimeTicks& renderer_before_unload_end_time) {}
 
   // PlzNavigate
   // Returns whether there is an ongoing navigation waiting for the BeforeUnload
   // event to execute in the renderer process.
   virtual bool IsWaitingForBeforeUnloadACK(FrameTreeNode* frame_tree_node);
 
  protected:
   friend class base::RefCounted<Navigator>;
   virtual ~Navigator() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_NAVIGATOR_H_