Factor out preference-in-storage check to overridable method.

Change-Id: I2fff3192802f8a180330fda66388eda394334a5a
Memory leak: parseObbFile.footer

Change-Id: Ia9e005e63fad7ab364f6c2c80cb98ec98f89b470
Signed-off-by: You Kim <you.kim72@gmail.com>