Random fixes discovered when looking through CL 11824035.

tests/language/double_to_string_as_exponential2_test.dart

 // Copyright (c) 2012, 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.
 // Test basic integer operations.
 
 main() {
-  // TODO(floitsch): verify that returned exception is correct type.
   Expect.throws(() => (1.0).toStringAsExponential(-1),
                 (e) => e is RangeError);
   Expect.throws(() => (1.0).toStringAsExponential(21),
                 (e) => e is RangeError);
   Expect.throws(() => (1.0).toStringAsExponential(1.5),
                 (e) => e is ArgumentError || e is TypeError);
   Expect.throws(() => (1.0).toStringAsExponential("string"),
                 (e) => e is ArgumentError || e is TypeError);
   Expect.throws(() => (1.0).toStringAsExponential("3"),
                 (e) => e is ArgumentError || e is TypeError);
 }