Add a typeannotation and a missing argument to remove warnings.

lib/compiler/implementation/unparse_validator.dart

Index: lib/compiler/implementation/unparse_validator.dart
diff --git a/lib/compiler/implementation/unparse_validator.dart b/lib/compiler/implementation/unparse_validator.dart
index 2a54f568e3ac9240b995233c33860e090b3b662e..5004894e6e1f7a3bb043446e63fd1e790d944cdb 100644
--- a/lib/compiler/implementation/unparse_validator.dart
+++ b/lib/compiler/implementation/unparse_validator.dart
@@ -11,7 +11,8 @@ class ValidatorListener implements DiagnosticListener {
     assert(token !== null);
     SourceSpan.withOffsets(token, token, (beginOffset, endOffset) {
         String errorMessage =
-            sourceFile.getLocationMessage(reason, beginOffset, endOffset, true);
+            sourceFile.getLocationMessage(reason, beginOffset, endOffset, true,
+                                          (s) => s /* no color */);
         print(errorMessage);
     });
     throw new CompilerCancelledException(reason);