InstantExtended: record Instant NTP load times.

chrome/browser/ui/search/search_tab_helper.cc

Index: chrome/browser/ui/search/search_tab_helper.cc
diff --git a/chrome/browser/ui/search/search_tab_helper.cc b/chrome/browser/ui/search/search_tab_helper.cc
index f779ede42c8d09490d70fa5e6a7c95ac23e7be9f..a12e8c513302ee0c3726a422dbe9032840f58cef 100644
--- a/chrome/browser/ui/search/search_tab_helper.cc
+++ b/chrome/browser/ui/search/search_tab_helper.cc
@@ -29,6 +29,7 @@
 #include "chrome/browser/ui/omnibox/omnibox_popup_model.h"
 #include "chrome/browser/ui/omnibox/omnibox_view.h"
 #include "chrome/browser/ui/search/search_ipc_router_policy_impl.h"
+#include "chrome/browser/ui/tab_contents/core_tab_helper.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/tabs/tab_strip_model_utils.h"
 #include "chrome/browser/ui/webui/ntp/ntp_user_data_logger.h"
@@ -123,6 +124,19 @@ void UpdateLocationBar(content::WebContents* contents) {
 #endif
 }
 
+// Called when an NTP finishes loading. If the load start time was noted,
+// calculates and logs the total load time.
+void RecordNewTabLoadTime(content::WebContents* contents) {
+  CoreTabHelper* core_tab_helper = CoreTabHelper::FromWebContents(contents);
+  if (core_tab_helper->new_tab_start_time().is_null())
+    return;
+
+  base::TimeDelta duration =
+      base::TimeTicks::Now() - core_tab_helper->new_tab_start_time();
+  UMA_HISTOGRAM_TIMES("Tab.NewTabOnload", duration);
+  core_tab_helper->set_new_tab_start_time(base::TimeTicks());

[Jered, 2014/01/02 20:12:41]

Why are you resetting the start time here?

[samarth, 2014/01/04 01:22:38]

This is because not all code paths that open the NTP record the start time
(IIRC, only if you use ctrl+T or if you click on the new tab button).  And we
use the existence of a non-null start here to decide whether the start time was
recorded. So if we didn't clear here and then opened an NTP in the same tab
again by typing chrome://newtab, it would record the wrong time.

+}
+
 }  // namespace
 
 SearchTabHelper::SearchTabHelper(content::WebContents* web_contents)
@@ -290,8 +304,12 @@ void SearchTabHelper::DidFinishLoad(
     const GURL&  /* validated_url */,
     bool is_main_frame,
     content::RenderViewHost* /* render_view_host */) {
-  if (is_main_frame)
+  if (is_main_frame) {
+    if (chrome::IsInstantNTP(web_contents_))
+      RecordNewTabLoadTime(web_contents_);
+
     DetermineIfPageSupportsInstant();
+  }
 }
 
 void SearchTabHelper::NavigationEntryCommitted(