Adding histograms for better Omnibox prerender performance tracking.

chrome/browser/prerender/prerender_histograms.h

Index: chrome/browser/prerender/prerender_histograms.h
diff --git a/chrome/browser/prerender/prerender_histograms.h b/chrome/browser/prerender/prerender_histograms.h
index 53c9df1aa93f1867a65f22c1e49a006211ab1c3e..2d1fb339dd0f2a31e61b0fd3af7303baaa35e59f 100644
--- a/chrome/browser/prerender/prerender_histograms.h
+++ b/chrome/browser/prerender/prerender_histograms.h
@@ -55,6 +55,13 @@ class PrerenderHistograms {
   // To be called when a new prerender is added.
   void RecordPrerender(Origin origin, const GURL& url);
 
+  // Called when a prerender is added with an Omnibox origin.
+  void RecordPrerenderFromOmnibox() const;
+
+  // Called when we swap in a prerender. Checks if the origin is Omnibox before
+  // recording the count.
+  void RecordOmniboxUsedPrerender(Origin origin) const;
+
  private:
   base::TimeTicks GetCurrentTimeTicks() const;