Change the stub for file_util::EvictFileFromSystemCache
Change the stub for file_util::EvictFileFromSystemCache

I don't think there is a way to get something out of the UBC once it's in,
so for now I'm just making this api return true so it won't fail unittests.
I have email out to Amit incase he has any ideas.

Review URL: http://codereview.chromium.org/42333

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@11961 0039d316-1c4b-4281-b951-d872f2087c98

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