Fix double-initialization of CComModule.

ui/base/win/atl_module.h

+// 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.
+
+#ifndef UI_BASE_WIN_ATL_MODULE_H_
+#define UI_BASE_WIN_ATL_MODULE_H_
+#pragma once
+
+#include <atlbase.h>
+#include <atlcom.h>
+
+#include "base/basictypes.h"
+
+namespace ui {
+namespace win {
+
+// Ensure that we have exactly one ATL module registered. It's safe to
+// call this more than once. ATL functions will crash if there's no
+// ATL module registered, or if you try to register two of them, so
+// dynamically registering one if needed makes it much easier for us
+// to support different build configurations like multi-dll without
+// worrying about which side of a module boundary each ATL module object
+// belongs on.
+//
+// This function must be implemented in this header file rather than a
+// source file so that it's inlined into the module where it's included,
+// rather than in the "ui" module.
+static void CreateATLModuleIfNeeded() {
+  if (_pAtlModule == NULL) {
+    // This creates the module and automatically updates _pAtlModule.
+    CR_DEFINE_STATIC_LOCAL(CComModule, module, ());
+  }
+}
+
+}  // namespace win
+}  // namespace ui
+
+#endif  // UI_BASE_WIN_ATL_MODULE_H_