Fix GetCachedFile(use_root=True)...

Fix GetCachedFile(use_root=True)

Fix GetCachedFile() to skip local mods when use_root is True. The files
that exist in the root of the tree don't even seem to exist in the normal
source checkouts, and we were looking at a different file as a result.

  BUG=none
  R=maruel@chromium.org
  TEST=locally modify a PRESUBMIT.py file and look for duplicate results. 
    If you get duplicates, this didn't fix it


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=31586

[M-A Ruel, 2009-11-10 13:49:37]

lgtm

[M-A Ruel, 2009-11-10 13:50:05]

lgtm

http://codereview.chromium.org/379021