Rename class AssertError to AssertionError in the VM (fix issue 119).

tests/language/src/AssertTest.dart

-// Copyright (c) 2011, 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.
-// VMOptions=--enable_asserts
-//
-// Dart test program testing assert statements.
-
-class AssertTest {
-  static test() {
-    int i = 0;
-    try {
-      assert(false);
-    } catch (AssertError error) {
-      i = 1;
-      Expect.equals("false", error.failedAssertion);
-      int pos = error.url.lastIndexOf("/", error.url.length);
-      if (pos == -1) {
-        pos = error.url.lastIndexOf("\\", error.url.length);
-      }
-      String subs = error.url.substring(pos + 1, error.url.length);
-      Expect.equals("AssertTest.dart", subs);
-      Expect.equals(12, error.line);
-      Expect.equals(14, error.column);
-    }
-    return i;
-  }
-  static testClosure() {
-    int i = 0;
-    try {
-      assert(() => false);
-    } catch (AssertError error) {
-      i = 1;
-      Expect.equals("() => false", error.failedAssertion);
-      int pos = error.url.lastIndexOf("/", error.url.length);
-      if (pos == -1) {
-        pos = error.url.lastIndexOf("\\", error.url.length);
-      }
-      String subs = error.url.substring(pos + 1, error.url.length);
-      Expect.equals("AssertTest.dart", subs);
-      Expect.equals(30, error.line);
-      Expect.equals(14, error.column);
-    }
-    return i;
-  }
-
-  static testMain() {
-    Expect.equals(1, test());
-    Expect.equals(1, testClosure());
-  }
-}
-
-main() {
-  AssertTest.testMain();
-}