Move AppendFile and *CurrentDirectory to the base namespace.

This moves AppendFile, GetCurrentDirectory, and SetCurrentDirectory to the base namespace.

TBR=jam

Review URL: https://codereview.chromium.org/177923007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256309 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256309