[HttpWebRequest] Ignore Transfer-Encoding when there's no content.

	If the transfer encoding was set to chunked, we tried to read even when
	the response might known to have no content. This led to timeouts.

	Fixes bug #686371.

mcs/class/System/System.Net/WebConnection.cs

@@ -466,9 +466,12 @@ static void ReadDone (IAsyncResult result)
 			cnc.position = 0;
 
 			WebConnectionStream stream = new WebConnectionStream (cnc);
+			bool expect_content = ExpectContent (data.StatusCode, data.request.Method);
+			string tencoding = null;
+			if (expect_content)
+				tencoding = data.Headers ["Transfer-Encoding"];
 
-			string contentType = data.Headers ["Transfer-Encoding"];
-			cnc.chunkedRead = (contentType != null && contentType.IndexOf ("chunked", StringComparison.OrdinalIgnoreCase) != -1);
+			cnc.chunkedRead = (tencoding != null && tencoding.IndexOf ("chunked", StringComparison.OrdinalIgnoreCase) != -1);
 			if (!cnc.chunkedRead) {
 				stream.ReadBuffer = cnc.buffer;
 				stream.ReadBufferOffset = pos;
@@ -493,14 +496,16 @@ static void ReadDone (IAsyncResult result)
 
 			data.stream = stream;
 
-			if (!ExpectContent (data.StatusCode) || data.request.Method == "HEAD")
+			if (!expect_content)
 				stream.ForceCompletion ();
 
 			data.request.SetResponseData (data);
 		}
 
-		static bool ExpectContent (int statusCode)
+		static bool ExpectContent (int statusCode, string method)
 		{
+			if (method == "HEAD")
+				return false;
 			return (statusCode >= 200 && statusCode != 204 && statusCode != 304);
 		}