Revert "Wipe and re-create database on downgrade."

This reverts commit 1cd1f7f822123287f9b8b4e1d24d6e3b354fd915.
Revert "Memory leak in IInputMethodSessionWrapper executeMessage"

This reverts commit e0c32a151cd411af2a7c82461da06d078c2c9a3d.
Revert "Fix NullpointerException in MediaMetadataRetriever"

This reverts commit a61869d68ccfcb1700ba30521307d6e0effc4aa4.