Add javadoc saying that wake locks are ref counted by default.
Add javadoc saying that wake locks are ref counted by default.

Bug: 3012561
Change-Id: I441a42fdb12ba6d87d6f5a49463d6ddcc300acb7

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