Remove uses of PropVariantTo*; removing the need to DelayLoad propsys.dll.

base/win/scoped_propvariant.h

+// Copyright (c) 2013 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 BASE_WIN_SCOPED_PROPVARIANT_H_
+#define BASE_WIN_SCOPED_PROPVARIANT_H_
+
+#include <propidl.h>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+
+namespace base {
+namespace win {
+
+// A PROPVARIANT that is automatically initialized and cleared upon respective
+// construction and destruction of this class.
+class ScopedPropVariant {
+ public:
+  ScopedPropVariant() {
+    PropVariantInit(&pv_);
+  }
+
+  ~ScopedPropVariant() {
+    Reset();
+  }
+
+  // Returns a pointer to the underlying PROPVARIANT for use as an out param in
+  // a function call.
+  PROPVARIANT* Receive() {
+    DCHECK_EQ(pv_.vt, VT_EMPTY);
+    return &pv_;
+  }
+
+  // Clears the instance to prepare it for re-use (e.g., via Receive).
+  void Reset() {
+    if (pv_.vt != VT_EMPTY) {
+      HRESULT result = PropVariantClear(&pv_);
+      DCHECK_EQ(result, S_OK);
+    }
+  }
+
+  const PROPVARIANT& get() const { return pv_; }
+
+  const PROPVARIANT* operator&() const { return &pv_; }
+
+ private:
+  PROPVARIANT pv_;
+
+  // Comparison operators for ScopedPropVariant are not supported at this point.
+  bool operator==(const ScopedPropVariant&) const;
+  bool operator!=(const ScopedPropVariant&) const;
+  DISALLOW_COPY_AND_ASSIGN(ScopedPropVariant);
+};
+
+}  // namespace win
+}  // namespace base
+
+#endif  // BASE_WIN_SCOPED_PROPVARIANT_H_