Adding the main configuration variable management class.
This is the heart of the cr tool, it controls everything else that happens.

BUG=316397

Review URL: https://codereview.chromium.org/64203003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234869 0039d316-1c4b-4281-b951-d872f2087c98
[Files.app] Set the minimum size of file dialog as 320px x 240px

BUG=310818
TEST=manually tested

Review URL: https://codereview.chromium.org/70673003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234870 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234870