Merge to XFA: Make a bunch of JBig2 classes independent of CJBig2_Object.

TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1319713003 .

(cherry picked from commit 800bf5ac07305ccf9c9522c8c76f728a4fd99da5)

Review URL: https://codereview.chromium.org/1332153002 .