getDuration can be only called after prepared.
getDuration can be only called after prepared.

bug:5816130
Change-Id: I4f264ef612995bc4f7bc3e378893ed9491423fdc

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base