Update docs for DisplayMetrics pixel size fields
Update docs for DisplayMetrics pixel size fields

Update docs to reflect that values in fields store sizes available for
application (not full screen size).

Bug: 27449789
Change-Id: I92f7552a92fa1b66c5eba4cf28693528cbff21d3

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