Implement --fatal=errors.

pkg/front_end/lib/src/fasta/messages.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library fasta.messages;
 
 import 'package:kernel/ast.dart' show
     Location,
     Program;
 
 import 'util/relativize.dart' show
     relativizeUri;
 
 import 'compiler_context.dart' show
     CompilerContext;
 
 import 'errors.dart' show
     InputError;
 
 import 'colors.dart' show
     cyan,
     magenta;
 
 const bool hideNits = false;
 
 const bool hideWarnings = false;
 
+bool get areErrorsFatal => CompilerContext.current.options.areErrorsFatal;
+
+bool get areNitsFatal => CompilerContext.current.options.areNitsFatal;
+
+bool get areWarningsFatal => CompilerContext.current.options.areWarningsFatal;
+
+bool get isVerbose => CompilerContext.current.options.verbose;
+
 void warning(Uri uri, int charOffset, String message) {
   if (hideWarnings) return;
   print(format(uri, charOffset, colorWarning("Warning: $message")));
-  if (CompilerContext.current.options.areWarningsFatal) {
-    if (CompilerContext.current.options.verbose) print(StackTrace.current);
+  if (areWarningsFatal) {
+    if (isVerbose) print(StackTrace.current);
     throw new InputError(
         uri, charOffset, "Compilation aborted due to fatal warnings.");
   }
 }
 
 void nit(Uri uri, int charOffset, String message) {
   if (hideNits) return;
   print(format(uri, charOffset, colorNit("Nit: $message")));
-  if (CompilerContext.current.options.areNitsFatal) {
-    if (CompilerContext.current.options.verbose) print(StackTrace.current);
+  if (areNitsFatal) {
+    if (isVerbose) print(StackTrace.current);
     throw new InputError(
         uri, charOffset, "Compilation aborted due to fatal nits.");
   }
 }
 
 String colorWarning(String message) {
   // TODO(ahe): Colors need to be optional. Doesn't work well in Emacs or on
   // Windows.
   return magenta(message);
 }
@@ skipping 12 matching lines @@
     return "$position: $message";
   } else {
     return message;
   }
 }
 
 Location getLocation(String path, int charOffset) {
   return new Program(null, CompilerContext.current.uriToSource)
       .getLocation(path, charOffset);
 }