Add request_id to HttpRequestInfo and pass it to the NetworkDelegate for events.

net/http/http_request_info.h

Index: net/http/http_request_info.h
diff --git a/net/http/http_request_info.h b/net/http/http_request_info.h
index 7c73aa62f003060beab93f71b3a01fe1da0c6e3b..58b111ec4cac9e66655b5052e3e9d21bf064bc4b 100644
--- a/net/http/http_request_info.h
+++ b/net/http/http_request_info.h
@@ -52,6 +52,10 @@ struct HttpRequestInfo {
 
   // The motivation behind this request.
   RequestMotivation motivation;
+
+  // An optional globally unique identifier for this request for use by the
+  // consumer. 0 is invalid.
+  uint64 request_id;
 };
 
 }  // namespace net