Re-try r29078: Remove some deprecated file_util wstring functions.

With the previous patch, the try bots failed with mysterious messages, so I ignored them, patched it into my windows box and tested it there manually, and found no problems. As it turns out, the try failures were real :(. But nsylvain and I found the problem: the behavior of file_util::GetDirectoryFromPath() differs from DirName() when the path is empty (officially, GetDirectoryFromPath is not supposed to support non-absolute paths, but that is not enforced).

Here is a green win try result: http://build.chromium.org/buildbot/try-server/builders/win/builds/3705
mac: http://build.chromium.org/buildbot/try-server/builders/mac/builds/3491
linux: http://build.chromium.org/buildbot/try-server/builders/linux/builds/3466

I also applied this patch locally in Windows to test that it doesn't break the chrome frame compile or tests, since that's not covered by the trybots yet.
Review URL: http://codereview.chromium.org/271099

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@29094 0039d316-1c4b-4281-b951-d872f2087c98