Don't dump a stack trace on the user if the formatter had bad output.

test/formatter_test.dart

 // Copyright (c) 2014, 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.
 
 @TestOn("vm")
 library dart_style.test.formatter_test;
 
 import 'dart:io';
 import 'dart:mirrors';
 
@@ skipping 114 matching lines @@
       expect(
           new DartFormatter(lineEnding: "\r\n").formatStatement('  """first\r\n'
               'second\r\n'
               'third"""  ;'),
           equals('"""first\r\n'
               'second\r\n'
               'third""";'));
     });
   });
 
-  test('throws a FormatterException on non-whitespace changes', () {
+  test('throws an UnexpectedOutputException on non-whitespace changes', () {
     // Use an invalid line ending character to ensure the formatter will
     // attempt to make non-whitespace changes.
     var formatter = new DartFormatter(lineEnding: '%');
     expect(() => formatter.format("var i = 1;"),
-        throwsA(new isInstanceOf<FormatException>()));
+        throwsA(new isInstanceOf<UnexpectedOutputException>()));
   });
 }
 
 /// Run tests defined in "*.unit" and "*.stmt" files inside directory [name].
 void testDirectory(String name) {
   var indentPattern = new RegExp(r"^\(indent (\d+)\)\s*");
 
   // Locate the "test" directory. Use mirrors so that this works with the test
   // package, which loads this suite into an isolate.
   var testDir = p.dirname(currentMirrorSystem()
@@ skipping 97 matching lines @@
   source = source.replaceAll("‹", "");
 
   var end = source.indexOf("›");
   source = source.replaceAll("›", "");
 
   return new SourceCode(source,
       isCompilationUnit: isCompilationUnit,
       selectionStart: start == -1 ? null : start,
       selectionLength: end == -1 ? null : end - start);
 }