Fix host-checked mode error in dart2js by removing bad assertion.

tests/language/aborting_switch_case_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.
+
+// Regression test for dart2js that used to be confused when inlining
+// method that always aborts in a switch case.
+
+import "package:expect/expect.dart";
+
+foo() { throw 42; }
+
+main() {
+  var exception;
+  try {
+    switch (42) {
+      case 42:
+        foo();
+        foo();
+        break;
+    }
+  } catch (e) {
+    exception = e;
+  }
+  Expect.equals(42, exception);
+}