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>
+
+namespace base {
+namespace win {
+
+// A PROPVARIANT that is automatically initialized and cleared upon respective
+// construction and destruction of this class.
+class ScopedPropVariant {

[grt (UTC plus 2), 2013/01/09 14:30:10]

it'd be nice if this scoper was safe to use. as it is, one could use operator&
multiple times and leak. i suggest replacing operator& with a Receive() that has
a DCHECK_EQ(pv_.vt, VT_EMPTY); see, for example, base/win/scoped_comptr.h.

[grt (UTC plus 2), 2013/01/09 16:06:16]

A Reset() method that calls PropVariantClear would be useful, too.

[gab, 2013/01/09 20:43:39]

Ah good point, done.

[gab, 2013/01/09 20:43:39]

Done.

+ public:
+  ScopedPropVariant() {
+    PropVariantInit(&pv_);
+  }
+  ~ScopedPropVariant() {
+    PropVariantClear(&pv_);
+  }
+
+  PROPVARIANT* operator&() {
+    return &pv_;
+  }
+
+  // Allow direct read-only access to the members of |pv_| with the -> operator.
+  const PROPVARIANT* operator->() const {

[grt (UTC plus 2), 2013/01/09 14:30:10]

a conversion function would be a nice fit:

  operator const PROPVARIANT&() const { return pv_; }

this allows consumers of ScopedPropVariant to use it exactly as a PROPVARIANT.

you may also want:

  const PROPVARIANT* operator&() const { return &pv_; }

so that it can be passed to funcs that require a pointer.

[gab, 2013/01/09 20:43:39]

This doesn't work directly: i.e. pv_app_it.vt still won't compile. I can either
use the -> operator instead (as I'm currently doing, but that feels hacky) or I
can add a 
  const PROPVARIANT& get() const { return pv_; }
method and use pv_app_id.get().vt (which I also find ugly...).

Any other clever C++ ideas?
Done.

[grt (UTC plus 2), 2013/01/10 03:24:05]

Doh!
Of these options, I prefer the get() method over operator->.
Inheritance rather than encapsulation would do it, but that would open the door
to direct manipulation of the underlying PROPVARIANT so it's probably a bad
idea.

[gab, 2013/01/10 15:30:42]

Ok change removed operator->, added get() method.

+    return &pv_;
+  }
+
+ private:
+  PROPVARIANT pv_;
+};
+
+}  // namespace win
+}  // namespace base
+
+#endif  // BASE_WIN_SCOPED_PROPVARIANT_H_