Don't convert HEAD requests to GETs on 303 redirects.

net/url_request/url_request.cc

Index: net/url_request/url_request.cc
===================================================================
--- net/url_request/url_request.cc	(revision 107563)
+++ net/url_request/url_request.cc	(working copy)
@@ -695,15 +695,16 @@
     return ERR_UNSAFE_REDIRECT;
   }
 
-  // For 303 redirects, all request methods are converted to GETs, as per RFC
-  // 2616.  The latest httpbis draft also allows POST requests to be converted
-  // to GETs when following 301/302 redirects for historical reasons.  Most
-  // major browsers do this and so shall we.  The RFC says to prompt the user
-  // to confirm the generation of new requests, other than GET and HEAD
+  // For 303 redirects, all request methods except HEAD are converted to GET,
+  // as per RFC 2616.  The exception for HEADs is not explicitly stated, but
+  // is implied.  The latest httpbis draft also allows POST requests to be
+  // converted to GETs when following 301/302 redirects for historical reasons.
+  // Most major browsers do this and so shall we.  The RFC says to prompt the
+  // user to confirm the generation of new requests, other than GET and HEAD
   // requests, but IE omits these prompts and so shall we.
   // See:  http://greenbytes.de/tech/webdav/draft-ietf-httpbis-p2-semantics-latest.html#status.3xx
   bool was_post = method_ == "POST";
-  if (http_status_code == 303 ||
+  if ((http_status_code == 303 && method_ != "HEAD") ||
       ((http_status_code == 301 || http_status_code == 302) && was_post)) {
     method_ = "GET";
     upload_ = NULL;