Implement --fatal=errors.

pkg/front_end/lib/src/fasta/compiler_command_line.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.compiler_command_line;
 
 import 'dart:io' show
     exit;
 
 import 'command_line.dart' show
@@ skipping 56 matching lines @@
   Uri get platform {
     return options.containsKey("--compile-sdk")
         ? null
         : options["--platform"] ?? Uri.base.resolve("platform.dill");
   }
 
   Set<String> get fatal {
     return new Set<String>.from(options["--fatal"] ?? <String>[]);
   }
 
-  bool get areErrorsFatal => fatal.contains("errors");
+  bool get errorsAreFatal => fatal.contains("errors");
 
-  bool get areWarningsFatal => fatal.contains("warnings");
+  bool get warningsAreFatal => fatal.contains("warnings");
 
-  bool get areNitsFatal => fatal.contains("nits");
+  bool get nitsAreFatal => fatal.contains("nits");
 
   static dynamic withGlobalOptions(String programName, List<String> arguments,
       dynamic f(CompilerContext context)) {
     return CompilerContext.withGlobalOptions(
         new CompilerCommandLine(programName, arguments), f);
   }
 
   static CompilerCommandLine forRootContext() {
     return new CompilerCommandLine("", [""]);
   }
@@ skipping 74 matching lines @@
     Compile the SDK from scratch instead of reading it from 'platform.dill'.
 
   --fatal=errors
   --fatal=warnings
   --fatal=nits
     Makes messages of the given kinds fatal, that is, immediately stop the
     compiler with a non-zero exit-code. In --verbose mode, also display an
     internal stack trace from the compiler. Multiple kinds can be separated by
     commas, for example, --fatal=errors,warnings.
 """;