Revert "Fix compilation of Enum on JDK 7"

This reverts commit a4ec0cd6f0cefced7f5b0e23b313bd66e6890570.
Fix Java 7 build.

See http://bugs.sun.com/view_bug.do?bug_id=6904536
Bug: 8992787

(cherry-picked from a9a297845620cfe56bbe3b9f8de1331b7ec54574)

Change-Id: I14ff930b02914563493fbcd971f3393fa0c12105