Make base compile with no "using base::FilePath".

Make base compile with no "using base::FilePath".

For base .cc files not using the base namespace, I added a using since theses
files should be moved to the base namespace, and then explicit qualification
will no longer be necessary.

Original review URL: https://codereview.chromium.org/12226121
(reland of r182040).
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=182916

[brettw, 2013-02-15 21:02:05]

Sorry I forgot to upload the original patch as a base.

The only changes are removing "base::" from file_path.cc and moving the PrintTo
implementation in file_path.cc out of the base namespace (to match the header).

[jar (doing other things), 2013-02-16 00:55:14]

lgtm