Add metrics for calculating precision/recall of link navigation pre-connect triggers.

chrome/browser/net/predictor.h

Index: chrome/browser/net/predictor.h
diff --git a/chrome/browser/net/predictor.h b/chrome/browser/net/predictor.h
index b56a62bdf913840cb937999a953b3be0569b9036..a1f44150c7321eb5415c7e186e9e68d2dcfb472f 100644
--- a/chrome/browser/net/predictor.h
+++ b/chrome/browser/net/predictor.h
@@ -238,7 +238,14 @@ class Predictor {
                                UrlInfo::ResolutionMotivation motivation,
                                int count);
 
-  void RecordPreconnectNavigationStats(const GURL& url);
+  // May be called from either the IO or UI thread and will PostTask
+  // to the IO thread if necessary.
+  void RecordPreconnectTrigger(const GURL& url);
+
+  void RecordPreconnectTriggerOnIOThread(const GURL& url);
+
+  void RecordPreconnectNavigationStat(const GURL& url,
+                                      const GURL& original_url);
 
   // ------------- End IO thread methods.
 
@@ -509,7 +516,8 @@ class Predictor {
   // The time when the last preconnection was requested to a search service.
   base::TimeTicks last_omnibox_preconnect_;
 
-  TimedCache recent_preconnects_;
+  class PreconnectUsage;
+  scoped_ptr<PreconnectUsage> preconnect_usage_;
 
   // For each URL that we might navigate to (that we've "learned about")
   // we have a Referrer list. Each Referrer list has all hostnames we might