Record start up latency of DOM distiller viewer

chrome/browser/dom_distiller/tab_utils.cc

 // 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.
 
 #include "chrome/browser/dom_distiller/tab_utils.h"
 
 #include <utility>
 
 #include "base/message_loop/message_loop.h"
 #include "chrome/browser/dom_distiller/dom_distiller_service_factory.h"
@@ skipping 88 matching lines @@
 
 void SelfDeletingRequestDelegate::TakeViewerHandle(
     std::unique_ptr<ViewerHandle> viewer_handle) {
   viewer_handle_ = std::move(viewer_handle);
 }
 
 // Start loading the viewer URL of the current page in |web_contents|.
 void StartNavigationToDistillerViewer(content::WebContents* web_contents,
                                       const GURL& url) {
   GURL viewer_url = dom_distiller::url_utils::GetDistillerViewUrlFromUrl(
-      dom_distiller::kDomDistillerScheme, url);
+      dom_distiller::kDomDistillerScheme, url,
+      (base::TimeTicks::Now() - base::TimeTicks()).InMilliseconds());

[mdjones, 2016/05/31 17:26:25]

I'm not sure I understand why the subtraction is needed.

[wychen, 2016/05/31 17:59:26]

TimeTicks cannot be directly converted to int. TimeDelta can.

   content::NavigationController::LoadURLParams params(viewer_url);
   params.transition_type = ui::PAGE_TRANSITION_AUTO_BOOKMARK;
   web_contents->GetController().LoadURLWithParams(params);
 }
 
 void MaybeStartDistillation(
     std::unique_ptr<SourcePageHandleWebContents> source_page_handle) {
   const GURL& last_committed_url =
       source_page_handle->web_contents()->GetLastCommittedURL();
   if (!dom_distiller::url_utils::IsUrlDistillable(last_committed_url))
@@ skipping 51 matching lines @@
   DCHECK(source_web_contents);
   DCHECK(destination_web_contents);
 
   std::unique_ptr<SourcePageHandleWebContents> source_page_handle(
       new SourcePageHandleWebContents(source_web_contents, false));
 
   MaybeStartDistillation(std::move(source_page_handle));
   StartNavigationToDistillerViewer(destination_web_contents,
                                    source_web_contents->GetLastCommittedURL());
 }