- Changed the algorithm from breadth-first to depth-first.
- Added infinite recursion support.
- Fixed From() of From() dependency.
- Fixed cross solution custom deps aliasing.
- Removed support code for old .gclient_entries format.
- Removed IsGitCheckout() in favor for a direct check for .git presence.

TEST=all test pass

Review URL: http://codereview.chromium.org/2867047

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@51760 0039d316-1c4b-4281-b951-d872f2087c98