Add field trial stats for alternate_protocol.

net/http/http_response_info.cc

Index: net/http/http_response_info.cc
===================================================================
--- net/http/http_response_info.cc	(revision 50874)
+++ net/http/http_response_info.cc	(working copy)
@@ -47,6 +47,10 @@
   // This bit is set if the request was fetched via an explicit proxy.
   RESPONSE_INFO_WAS_PROXY = 1 << 15,
 
+  // This bit is set if response could use alternate protocol. However, browser
+  // will ingore the alternate protocol if spdy is not enabled.
+  RESPONSE_INFO_WAS_ALTERNATE_PROTOCOL_AVAILABLE = 1 << 16,
+
   // TODO(darin): Add other bits to indicate alternate request methods.
   // For now, we don't support storing those.
 };
@@ -55,6 +59,7 @@
     : was_cached(false),
       was_fetched_via_spdy(false),
       was_npn_negotiated(false),
+      was_alternate_protocol_available(false),
       was_fetched_via_proxy(false) {
 }
 
@@ -119,6 +124,9 @@
 
   was_npn_negotiated = (flags & RESPONSE_INFO_WAS_NPN) != 0;
 
+  was_alternate_protocol_available =
+      (flags & RESPONSE_INFO_WAS_ALTERNATE_PROTOCOL_AVAILABLE) != 0;
+
   was_fetched_via_proxy = (flags & RESPONSE_INFO_WAS_PROXY) != 0;
 
   *response_truncated = (flags & RESPONSE_INFO_TRUNCATED) ? true : false;
@@ -144,6 +152,8 @@
     flags |= RESPONSE_INFO_WAS_SPDY;
   if (was_npn_negotiated)
     flags |= RESPONSE_INFO_WAS_NPN;
+  if (was_alternate_protocol_available)
+    flags |= RESPONSE_INFO_WAS_ALTERNATE_PROTOCOL_AVAILABLE;
   if (was_fetched_via_proxy)
     flags |= RESPONSE_INFO_WAS_PROXY;