Add the OFN_NOCHANGEDIR flag when opening the multiple file dialog
on Windows, to avoid changing the directory.  This allows directories
to be renamed or deleted after showing the dialog.

We already do this for other Windows file dialogs.  It looks
like the lack of the flag in this dialog was a bug when it
was initially added in https://codereview.chromium.org/14907.

BUG=238094
R=sky@chromium.org

Review URL: https://codereview.chromium.org/89473002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238174 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238174