Move more file_util functions to base namespace.

This moves DevicePathToDriveLetterPath, NormalizeToNativeFilePath, IsLink, and GetFileInfo.

This also removes some explicit "base::" usage in base files I touched.

TBR=jam

Review URL: https://codereview.chromium.org/105293002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238763 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238763
Mojo: Fix RawChannelPosixTest.OnReadMessage's writes to handle EINTR.

No one will ever see the bug in the test, but if I don't do it properly I'll
forget to do it elsewhere.

R=darin@chromium.org, darin

Review URL: https://codereview.chromium.org/103373002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238764 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238764