ParameterCanBeDemotedIssue: remove GetInheritanceDepth.

It has the potential for a stack overflow when there's cyclic inheritance.
The sorting already done by GetAllBaseTypes() should be good enough.

ICSharpCode.NRefactory.CSharp/Refactoring/CodeIssues/ParameterCanBeDemotedIssue/ParameterCanBeDemotedIssue.cs

@@ -145,7 +145,6 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 				var validTypes = 
 					(from type in possibleTypes
 					 where !tryResolve || TypeChangeResolvesCorrectly(parameter, rootResolutionNode, type)
-					 orderby GetInheritanceDepth(type) ascending
 					 select type).ToList();
 				if (validTypes.Any()) {
 					// don't demote an array to IList
@@ -185,16 +184,6 @@ namespace ICSharpCode.NRefactory.CSharp.Refactoring
 					});
 				}
 			}
-
-			int GetInheritanceDepth(IType declaringType)
-			{
-				var depth = 0;
-				foreach (var baseType in declaringType.DirectBaseTypes) {
-					var newDepth = GetInheritanceDepth(baseType);
-					depth = Math.Max(depth, newDepth);
-				}
-				return depth;
-			}
 		}
 
 		class TypeChangeValidationNavigator : IResolveVisitorNavigator