New TimeToFirstURLJob* navigation metrics now work with PlzNavigate.

content/browser/loader/navigation_url_loader_delegate.h

 // Copyright 2014 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_LOADER_NAVIGATION_URL_LOADER_DELEGATE_H_
 #define CONTENT_BROWSER_LOADER_NAVIGATION_URL_LOADER_DELEGATE_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 21 matching lines @@
   // made to the delegate. The response body is returned as a stream in
   // |body_stream|.
   virtual void OnResponseStarted(
       const scoped_refptr<ResourceResponse>& response,
       scoped_ptr<StreamHandle> body_stream) = 0;
 
   // Called if the request fails before receving a response. |net_error| is a
   // network error code for the failure.
   virtual void OnRequestFailed(int net_error) = 0;
 
+  // Called when a begin navigation request is handled, right before the

[davidben, 2015/02/02 22:33:57]

"Called when a begin navigation request is handled" seems a little weird.

[davidben, 2015/02/02 22:37:06]

Sorry, never finished this comment.

Perhaps:
// Called after the network request has begun on the IO thread at time
|timestamp|. This is just a thread hop but is to compare timing against the
pre-PlzNavigate codepath which didn't start the network request until after the
renderer was initialized.

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

Done.

+  // first potential network request happens, providing the |timestamp| when
+  // that happened in the IO thread.
+  virtual void NavigationRequested(base::TimeTicks timestamp) = 0;

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

nit: OnNavigationRequested? mainly to match the naming pattern of the methods
above.

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

Done.

+
  protected:
   NavigationURLLoaderDelegate() {}
   virtual ~NavigationURLLoaderDelegate() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NavigationURLLoaderDelegate);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_NAVIGATION_URL_LOADER_DELEGATE_H_