Add histograms that track how long it takes to open the new tab page.

chrome/browser/tab_contents/tab_contents.cc

 // Copyright (c) 2009 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/tab_contents/tab_contents.h"
 
 #include "app/l10n_util.h"
 #include "app/resource_bundle.h"
 #include "base/file_version_info.h"
 #include "base/process_util.h"
@@ skipping 1152 matching lines @@
   render_view_host()->PrintingDone(document_cookie, success);
 }
 
 bool TabContents::IsActiveEntry(int32 page_id) {
   NavigationEntry* active_entry = controller_.GetActiveEntry();
   return (active_entry != NULL &&
           active_entry->site_instance() == GetSiteInstance() &&
           active_entry->page_id() == page_id);
 }
 
+void TabContents::LogNewTabTime(const std::string& event_name) {
+  // Not all new tab pages get timed.  In those cases, we don't have a
+  // new_tab_start_time_.
+  if (new_tab_start_time_.is_null())
+    return;
+
+  base::TimeDelta duration = base::TimeTicks::Now() - new_tab_start_time_;
+  if (event_name == "NewTab.ScriptStart") {
+    UMA_HISTOGRAM_TIMES("NewTab.ScriptStart", duration);
+  } else if (event_name == "NewTab.DOMContentLoaded") {
+    UMA_HISTOGRAM_TIMES("NewTab.DOMContentLoaded", duration);
+  } else if (event_name == "NewTab.Onload") {
+    UMA_HISTOGRAM_TIMES("NewTab.Onload", duration);
+    // The new tab page has finished loading; reset it.
+    new_tab_start_time_ = base::TimeTicks();
+  }
+}
+
 // Notifies the RenderWidgetHost instance about the fact that the page is
 // loading, or done loading and calls the base implementation.
 void TabContents::SetIsLoading(bool is_loading,
                                LoadNotificationDetails* details) {
   if (is_loading == is_loading_)
     return;
 
   if (!is_loading) {
     load_state_ = net::LOAD_STATE_IDLE;
     load_state_host_.clear();
@@ skipping 1387 matching lines @@
 
     default:
       NOTREACHED();
   }
 }
 
 void TabContents::set_encoding(const std::string& encoding) {
   encoding_ = CharacterEncoding::GetCanonicalEncodingNameByAliasName(encoding);
 }