Remove JSONResultsGenerator class.

This class was only being using by the android build scripts, so I have
moved all of the logic into chromium's src/build/android/pylib/utils.

This removes the cross-repo dependency between chromium and blink webkitpy.

R=ojan@chromium.org
BUG=242206

Review URL: https://codereview.chromium.org/349533002

git-svn-id: svn://svn.chromium.org/blink/trunk@176892 bbb929c8-8fbe-4397-9dbb-9b2b20218538