Fix check for throwing NSM implementations.

tests/compiler/dart2js/no_such_method_enabled_test.dart

 // Copyright (c) 2015, 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.
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import 'compiler_helper.dart';
 
 dummyImplTest() {
   String source = """
@@ skipping 191 matching lines @@
   var compiler = compilerFor(source, uri);
   asyncTest(() => compiler.runCompiler(uri).then((_) {
     Expect.isTrue(compiler.backend.enabledNoSuchMethod);
     ClassElement clsA = findElement(compiler, 'A');
     Expect.isTrue(
         compiler.backend.noSuchMethodRegistry.otherImpls.contains(
             clsA.lookupMember('noSuchMethod')));
   }));
 }
 
+dummyImplTest10() {
+  String source = """
+class A {
+  noSuchMethod(Invocation x) {
+    throw new UnsupportedException();
+  }
+}
+main() {
+  print(new A().foo());
+}
+""";
+  Uri uri = new Uri(scheme: 'source');
+  var compiler = compilerFor(source, uri);
+  asyncTest(() => compiler.runCompiler(uri).then((_) {
+    Expect.isTrue(compiler.backend.enabledNoSuchMethod);
+    ClassElement clsA = findElement(compiler, 'A');
+    Expect.isTrue(
+        compiler.backend.noSuchMethodRegistry.throwingImpls.contains(
+            clsA.lookupMember('noSuchMethod')));
+  }));
+}
+
 main() {
   dummyImplTest();
   dummyImplTest2();
   dummyImplTest3();
   dummyImplTest4();
   dummyImplTest5();
   dummyImplTest6();
   dummyImplTest7();
   dummyImplTest8();
   dummyImplTest9();
+  dummyImplTest10();
 }