Fix compile error with Windows clang.

Fix compile error with Windows clang.

This change fixes the following errors shown during compile with
Windows clang:

error: cannot pass non-trivial object of type 'ATL::CComBSTR' to variadic function; expected type from format string was 'wchar_t *' [-Wnon-pod-varargs]

Original CL: https://codereview.chromium.org/1252913009/

BUG=https://code.google.com/p/google-breakpad/issues/detail?id=662

Committed: https://code.google.com/p/google-breakpad/source/detail?r=1494

[Will Harris, 2015-08-19 22:02:18]

wfh@chromium.org changed reviewers:
+ mark@chromium.org

[Will Harris, 2015-08-19 22:03:03]

committing on behalf of yyanagisawa@chromium.org

[Will Harris, 2015-08-19 22:28:21]

Committed patchset #1 (id:1) manually as r1494 (presubmit successful).