Improve support for multiselect list box accessibility on Windows.

base/win/iunknown_impl_unittest.cc

Index: base/win/iunknown_impl_unittest.cc
===================================================================
--- base/win/iunknown_impl_unittest.cc	(revision 0)
+++ base/win/iunknown_impl_unittest.cc	(revision 0)
@@ -0,0 +1,54 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/win/iunknown_impl.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace win {
+
+class TestIUnknownImplSubclass : public IUnknownImpl {
+ public:
+  TestIUnknownImplSubclass() {
+    ++instance_count;
+  }
+  virtual ~TestIUnknownImplSubclass() {
+    --instance_count;
+  }
+  static int instance_count;
+};
+
+// static
+int TestIUnknownImplSubclass::instance_count = 0;
+
+TEST(IUnknownImplTest, IUnknownImpl) {
+  EXPECT_TRUE(SUCCEEDED(::CoInitialize(NULL)));
+
+  {
+    EXPECT_EQ(0, TestIUnknownImplSubclass::instance_count);
+    IUnknown* u = new TestIUnknownImplSubclass();
+
+    EXPECT_EQ(1, TestIUnknownImplSubclass::instance_count);
+
+    EXPECT_EQ(2, u->AddRef());
+
+    IUnknown* other = NULL;
+    EXPECT_EQ(E_NOINTERFACE, u->QueryInterface(
+        IID_IDispatch, reinterpret_cast<void**>(&other)));
+    EXPECT_EQ(S_OK, u->QueryInterface(
+        IID_IUnknown, reinterpret_cast<void**>(&other)));
+    other->Release();
+
+    EXPECT_EQ(2, u->Release());
+    EXPECT_EQ(1, u->Release());
+    EXPECT_EQ(0, u->Release());
+    EXPECT_EQ(0, TestIUnknownImplSubclass::instance_count);
+  }
+
+  ::CoUninitialize();
+}
+
+}  // namespace win
+}  // namespace base