Merge _FindDependencies() back into __init__() now that __init__() is somewhat smaller.

R=dpranke@chromium.org
BUG=
TEST=


Review URL: http://codereview.chromium.org/8059011

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@103053 0039d316-1c4b-4281-b951-d872f2087c98