Add checks to DEBUG mode that no instance of URLRequest or URLFetcher survive...

net/url_request/url_request.h

Index: net/url_request/url_request.h
===================================================================
--- net/url_request/url_request.h	(revision 23063)
+++ net/url_request/url_request.h	(working copy)
@@ -9,6 +9,7 @@
 #include <string>
 #include <vector>
 
+#include "base/leak_tracker.h"
 #include "base/linked_ptr.h"
 #include "base/logging.h"
 #include "base/ref_counted.h"
@@ -592,6 +593,8 @@
   // this to determine which URLRequest to allocate sockets to first.
   int priority_;
 
+  base::LeakTracker<URLRequest> leak_tracker_;
+
   DISALLOW_COPY_AND_ASSIGN(URLRequest);
 };