TIF: add more documentation on Session.setOverlayViewEnabled().
TIF: add more documentation on Session.setOverlayViewEnabled().

Bug: 19916441
Change-Id: I56685a7f417541a02078c4b9e9d324e641ec3da5

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