Made getRedirectURI and getTransferEncoding return const reference.

Made getRedirectURI and getTransferEncoding in HttpResponse return
const reference.

src/HttpResponse.cc

@@ -172,7 +172,7 @@ void HttpResponse::processRedirect()
   }
 }
 
-std::string HttpResponse::getRedirectURI() const
+const std::string& HttpResponse::getRedirectURI() const
 {
   return httpHeader_->getFirst(HttpHeader::LOCATION);
 }
@@ -182,7 +182,7 @@ bool HttpResponse::isTransferEncodingSpecified() const
   return httpHeader_->defined(HttpHeader::TRANSFER_ENCODING);
 }
 
-std::string HttpResponse::getTransferEncoding() const
+const std::string& HttpResponse::getTransferEncoding() const
 {
   // TODO See TODO in getTransferEncodingStreamFilter()
   return httpHeader_->getFirst(HttpHeader::TRANSFER_ENCODING);

src/HttpResponse.h

@@ -82,11 +82,11 @@ public:
 
   void processRedirect();
 
-  std::string getRedirectURI() const;
+  const std::string& getRedirectURI() const;
 
   bool isTransferEncodingSpecified() const;
 
-  std::string getTransferEncoding() const;
+  const std::string& getTransferEncoding() const;
 
   SharedHandle<StreamFilter> getTransferEncodingStreamFilter() const;