Adding histograms for better Omnibox prerender performance tracking.

chrome/browser/prerender/prerender_manager.cc

Index: chrome/browser/prerender/prerender_manager.cc
diff --git a/chrome/browser/prerender/prerender_manager.cc b/chrome/browser/prerender/prerender_manager.cc
index 18093a932c96f1e72d12bfa15f0c789a2a624cd6..aabe51e21f89595271d214371f0994acc72e273b 100644
--- a/chrome/browser/prerender/prerender_manager.cc
+++ b/chrome/browser/prerender/prerender_manager.cc
@@ -358,6 +358,8 @@ bool PrerenderManager::AddPrerenderFromOmnibox(
       break;
   };
 
+  histograms_->RecordPrerenderFromOmnibox();
+
   return AddPrerender(origin, std::make_pair(-1, -1), url, GURL(),
                       session_storage_namespace);
 }
@@ -646,6 +648,8 @@ bool PrerenderManager::MaybeUsePrerenderedPage(TabContents* tab_contents,
   histograms_->RecordPerSessionCount(++prerenders_per_session_count_);
   prerender_contents->set_final_status(FINAL_STATUS_USED);
 
+  histograms_->RecordOmniboxUsedPrerender(prerender_contents->origin());
+
   new_render_view_host->Send(
       new ChromeViewMsg_SetIsPrerendering(new_render_view_host->routing_id(),
                                           false));