Use directive trivia classification method

src/Workspaces/CSharp/Portable/Classification/Worker_Preprocesser.cs

@@ -263,20 +263,16 @@ private void ClassifyPragmaWarningDirective(PragmaWarningDirectiveTriviaSyntax n
             AddClassification(node.WarningKeyword, ClassificationTypeNames.PreprocessorKeyword);
             AddClassification(node.DisableOrRestoreKeyword, ClassificationTypeNames.PreprocessorKeyword);
 
-            // Comments after a "#pragma warning" directive without any error codes are trailing trivia of the "disable"/"restore" token.
-            foreach (var syntaxTrivia in node.DisableOrRestoreKeyword.TrailingTrivia)
+            foreach (var nodeOrToken in node.ErrorCodes.GetWithSeparators())
             {
-                if (syntaxTrivia.Kind() == SyntaxKind.WhitespaceTrivia)
-                {
-                    // Skip the initial whitespace
-                    continue;
-                }
-                ClassifyToken(syntaxTrivia.Token);
+                ClassifyNodeOrToken(nodeOrToken);
             }
 
-            foreach (var nodeOrToken in node.ErrorCodes.GetWithSeparators())
+            if (node.ErrorCodes.Count == 0)
             {
-                ClassifyNodeOrToken(nodeOrToken);
+                // When there are no error codes, we need to classify the directive's trivia.
+                // (When there are error codes, ClassifyNodeOrToken above takes care of that.)
+                ClassifyDirectiveTrivia(node);
             }
         }