Move histograms and supporting code that don't belong in content out.

chrome/browser/ui/webui/metrics_handler.cc

Index: chrome/browser/ui/webui/metrics_handler.cc
===================================================================
--- chrome/browser/ui/webui/metrics_handler.cc	(revision 206723)
+++ chrome/browser/ui/webui/metrics_handler.cc	(working copy)
@@ -11,6 +11,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/browser/metrics/metric_event_duration_details.h"
+#include "chrome/browser/ui/tab_contents/core_tab_helper.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/user_metrics.h"
@@ -82,10 +83,12 @@
 
   // Not all new tab pages get timed. In those cases, we don't have a
   // new_tab_start_time_.
-  if (tab->GetNewTabStartTime().is_null())
+  CoreTabHelper* core_tab_helper = CoreTabHelper::FromWebContents(tab);
+  if (core_tab_helper->new_tab_start_time().is_null())

[Avi (use Gerrit), 2013/06/18 21:20:33]

Same comment repeatedly: when pulling stuff out into a tab helper, are we sure
that CoreTabHelper::FromWebContents won't be null?

[jam, 2013/06/18 21:28:43]

when would WebContents exist without a CoreTabHelper?

[Avi (use Gerrit), 2013/06/18 21:32:47]

Beats me; that's the lesson I learned.

You seem pretty sure that _these_ WebContents will have a CoreTabHelper. That's
probably true. Just keep an eye on crashes :)

[jam, 2013/06/18 22:44:27]

to be clear: I was asking you, not making a statement :) I have no idea if it'll
be null, I'm depending on tests + canary as I prefer not to add null checks if
I'm not sure they're needed.

[Avi (use Gerrit), 2013/06/19 04:43:36]

My method was assuming it was non-null, and fixing crashes as they showed up. :O

     return;
 
-  base::TimeDelta duration = base::TimeTicks::Now() - tab->GetNewTabStartTime();
+  base::TimeDelta duration =
+      base::TimeTicks::Now() - core_tab_helper->new_tab_start_time();
   MetricEventDurationDetails details(event_name,
       static_cast<int>(duration.InMilliseconds()));
 
@@ -96,7 +99,8 @@
   } else if (event_name == "Tab.NewTabOnload") {
     UMA_HISTOGRAM_TIMES("Tab.NewTabOnload", duration);
     // The new tab page has finished loading; reset it.
-    tab->SetNewTabStartTime(base::TimeTicks());
+    CoreTabHelper* core_tab_helper = CoreTabHelper::FromWebContents(tab);
+    core_tab_helper->set_new_tab_start_time(base::TimeTicks());
   } else {
     NOTREACHED();
   }