Merge pull request #1337 from Unity-Technologies/unity-master-fix-1276200

Grab part of fix from upstream change: https://github.com/mono/mono/p…

mcs/class/System/System.Net/WebResponseStream.cs

@@ -653,7 +653,7 @@ namespace System.Net
 					else
 						StatusDescription = string.Empty;
 
-					if (pos >= buffer.Size)
+					if (pos >= buffer.Offset)
 						return true;
 				}