Files.app: Remove path properties from EntryLocation.

Previously EntryLocation has path properties such as root path or virtual
path. But currently, we'd like to move to focut on Entry and avoid to operations
by using paths. This CL removes the path properties from EntryLocation.

BUG=323753
TEST=manually

Review URL: https://codereview.chromium.org/96273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237897 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237897