Fix static type warnings in language/null_test.

tests/language/null_test.dart

 // Copyright (c) 2013, 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.
 // Second dart test program.
 
 // VMOptions=--optimization-counter-threshold=5
 
 import "dart:mirrors";
 import "package:expect/expect.dart";
 
@@ skipping 19 matching lines @@
 class Generic2<T, S> {
   bool test(o) => new Generic<T>().test(o);
   T cast(o) => new Generic<T>().cast(o);
   Type get type => new Generic<T>().type;
 }
 
 // Magic incantation to avoid the compiler recognizing the constant values
 // at compile time. If the result is computed at compile time, the dynamic code
 // will not be tested.
 confuse(x) {
-  try { throw [x]; } catch (e) { return e[0]; }
+  try { throw [x]; } on dynamic catch (e) { return e[0]; }
   return 42;
 }
 
 void main() {
   for (int i = 0; i < 10; i++) {
     test();
   }
 }
 
 void test() {
@@ skipping 131 matching lines @@
   // cannot be extracted.
   // Currently fails in VM.
   Expect.equals(null.toString, obj.toString);
   Expect.equals(null.noSuchMethod, obj.noSuchMethod);
   Expect.equals(null.hashCode, obj.hashCode);
 
   var toString = null.toString;
   Expect.equals("null", toString());
   Expect.equals("null", Function.apply(toString, []));
 
-  Expect.throws(() => null.notDeclared());
+  Expect.throws(() => obj.notDeclared());
   var noSuchMethod = null.noSuchMethod;
   // Assing to "var" to prevent warning.
   var capture = new CaptureInvocationMirror();
   var mirror = capture.notDeclared();
   Expect.throws(() => noSuchMethod(mirror));
   Expect.throws(() => Function.apply(noSuchMethod, [mirror]));
 }
 
 
 class CaptureInvocationMirror {
   noSuchMethod(mirror) => mirror;
 }