Add a test for "is Object", fix try-catch of null

tests/language/src/IsObjectTest.dart

Index: tests/language/src/IsObjectTest.dart
diff --git a/tests/language/src/IsObjectTest.dart b/tests/language/src/IsObjectTest.dart
new file mode 100644
index 0000000000000000000000000000000000000000..6c3ba2e4715040365521ff09367151280258a047
--- /dev/null
+++ b/tests/language/src/IsObjectTest.dart
@@ -0,0 +1,46 @@
+// 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.
+// Dart test program for the "is" type test operator.
+
+testTryCatch(x) {
+  try {
+    throw x;
+    Expect.fail("Exception '$x' should've been thrown");
+  } catch (Object obj) {
+    Expect.equals(obj, x);
+  }
+}
+
+main() {
+  var evalCount = 0;
+  testEval(x) { evalCount++; return x; }
+
+  // Test that types that match JS primitive types compare correctly to Object
+  var x = 1;
+  Expect.isTrue(x is Object);
+  x = 'hi';
+  Expect.isTrue(x is Object);
+  x = true;
+  Expect.isTrue(x is Object);
+  x = null;
+  Expect.isTrue(x is Object);
+  var y;
+  Expect.isTrue(y is Object);
+
+  // Verify that operand is evaluated
+  Expect.isTrue(testEval(123) is Object);
+  Expect.equals(1, evalCount);
+  Expect.isTrue(testEval('world') is Object);
+  Expect.equals(2, evalCount);
+  Expect.isTrue(testEval(false) is Object);
+  Expect.equals(3, evalCount);
+  Expect.isTrue(testEval(null) is Object);
+  Expect.equals(4, evalCount);
+
+  // Verify that these objects are catchable
+  testTryCatch(444);
+  testTryCatch('abc');
+  testTryCatch(true);
+  testTryCatch(null);
+}