Stop using SHFileOperation from the disk cache code.
Stop using SHFileOperation from the disk cache code.

Using SHFileOperation to delete old cache files has the disadvantage that once in a while
somebody decides to perform COM operations assuming STA, and that doesn't work with the
worker pool.

BUG=1314744


git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@590 0039d316-1c4b-4281-b951-d872f2087c98

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