Print creator's call-stack on URLRequestContextGetter leak in Debug.

net/url_request/url_request_context_getter.h

Index: net/url_request/url_request_context_getter.h
diff --git a/net/url_request/url_request_context_getter.h b/net/url_request/url_request_context_getter.h
index 081c97c7004bbc0315c37ae5851ab9c88086eae5..5a415267c898439c3e0f1147eb96f0f9f8c94724 100644
--- a/net/url_request/url_request_context_getter.h
+++ b/net/url_request/url_request_context_getter.h
@@ -5,6 +5,7 @@
 #ifndef NET_URL_REQUEST_URL_REQUEST_CONTEXT_GETTER_H_
 #define NET_URL_REQUEST_URL_REQUEST_CONTEXT_GETTER_H_
 
+#include "base/debug/stack_trace.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
@@ -70,6 +71,10 @@ class NET_EXPORT URLRequestContextGetter
 
   base::ObserverList<URLRequestContextGetterObserver> observer_list_;
 
+#if !defined(NDEBUG)
+  base::debug::StackTrace created_at;
+#endif  // !defined(NDEBUG)
+
   DISALLOW_COPY_AND_ASSIGN(URLRequestContextGetter);
 };