Delete declaration of HttpComposeAttributes.

Was accidentally left over in cl
https://webrtc-review.googlesource.com/33361.

Bug: webrtc:6424
Tbr: deadbeef@webrtc.org
Change-Id: Ifbdfc77554d072b671fcec44e67d97e783ca43fa
Reviewed-on: https://webrtc-review.googlesource.com/34182
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21318}
diff --git a/rtc_base/httpcommon.h b/rtc_base/httpcommon.h
index b33d382..2897c5a 100644
--- a/rtc_base/httpcommon.h
+++ b/rtc_base/httpcommon.h
@@ -158,8 +158,6 @@
 
 typedef std::pair<std::string, std::string> HttpAttribute;
 typedef std::vector<HttpAttribute> HttpAttributeList;
-void HttpComposeAttributes(const HttpAttributeList& attributes, char separator,
-                           std::string* composed);
 void HttpParseAttributes(const char * data, size_t len,
                          HttpAttributeList& attributes);
 bool HttpHasAttribute(const HttpAttributeList& attributes,