More DropBoxManager javadoc love.
More DropBoxManager javadoc love.

Change-Id: I9b14f6905533e0af66bd64fc76352ed8fc365058

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