We were previously logging the text using printf("%S", bstr). This
converts the UTF-16 BSTR to a multibyte string using wctomb, which
uses the codepage for the current locale to perform the conversion.
The conversion was failing, causing printf to bail and truncate the
string. By converting to UTF-8 manually before logging, we avoid this
issue (and also end up with UTF-8 output, which is what the expected
results contain). We may have to do this in other places in DRT,
eventually.

Fixes <http://webkit.org/b/38849> REGRESSION (r59016):
plugins/set-status.html fails on Windows

Reviewed by Alexey Proskuryakov.

* DumpRenderTree/win/DumpRenderTree.cpp:
(toUTF8): Moved this here from FrameLoadDelegate. Renamed from
BSTRtoString.

* DumpRenderTree/win/DumpRenderTreeWin.h: Added declaration of toUTF8.

* DumpRenderTree/win/FrameLoadDelegate.cpp: Removed BSTRtoString.
(descriptionSuitableForTestResult): Updated for rename.

* DumpRenderTree/win/UIDelegate.cpp:
(UIDelegate::setStatusText): Convert the status bar text to UTF-8
before logging it so that Windows won't try (and fail) to convert it
to the current locale's codepage.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@59371 268f45cc-cd09-0410-ab3c-d52691b4dbfc