Add field trial stats for alternate_protocol.

net/url_request/url_request.h

Index: net/url_request/url_request.h
===================================================================
--- net/url_request/url_request.h	(revision 50874)
+++ net/url_request/url_request.h	(working copy)
@@ -371,7 +371,8 @@
   // Indicate if this response was fetched from disk cache.
   bool was_cached() const { return response_info_.was_cached; }
 
-  // Returns true if the URLRequest was delivered with SPDY.
+  // True if response could use alternate protocol. However, browser will
+  // ingore the alternate protocol if spdy is not enabled.
   bool was_fetched_via_spdy() const {
     return response_info_.was_fetched_via_spdy;
   }
@@ -382,6 +383,12 @@
     return response_info_.was_npn_negotiated;
   }
 
+  // Returns true if the URLRequest was delivered when the alertnate protocol
+  // is available.
+  bool was_alternate_protocol_available() const {
+    return response_info_.was_alternate_protocol_available;
+  }
+
   // Returns true if the URLRequest was delivered through a proxy.
   bool was_fetched_via_proxy() const {
     return response_info_.was_fetched_via_proxy;