Add the UMA recording recall of URLRequests preconnected.

net/base/network_delegate.h

Index: net/base/network_delegate.h
diff --git a/net/base/network_delegate.h b/net/base/network_delegate.h
index 9c2913d6e108d60f93face34b3e04e943627c529..1383da6d57fc21eb1ffa8582807a9c84d2dc2400 100644
--- a/net/base/network_delegate.h
+++ b/net/base/network_delegate.h
@@ -65,6 +65,7 @@ class NET_EXPORT NetworkDelegate : public base::NonThreadSafe {
   // functions mostly forward to the private virtuals. They also add some sanity
   // checking on parameters. See the corresponding virtuals for explanations of
   // the methods and their arguments.
+  void NotifyBeforePreconnect(const GURL& url);

[mmenke, 2013/05/22 17:58:43]

This is an interface for the network stack, in net/, to communicate with the
consumer (The browser).  We shouldn't have functions here just for non-src/net
functions to call.

[kouhei (in TOK), 2013/05/23 07:31:13]

ok.

   int NotifyBeforeURLRequest(URLRequest* request,
                              const CompletionCallback& callback,
                              GURL* new_url);
@@ -111,6 +112,9 @@ class NET_EXPORT NetworkDelegate : public base::NonThreadSafe {
   // member functions will be called by the respective public notification
   // member function, which will perform basic sanity checking.
 
+  // Called before a preconnect is processed.
+  virtual void OnBeforePreconnect(const GURL& url) {}
+
   // Called before a request is sent. Allows the delegate to rewrite the URL
   // being fetched by modifying |new_url|. |callback| and |new_url| are valid
   // only until OnURLRequestDestroyed is called for this request. Returns a net