From Android S, Storage Settings queries file sizes
from MediaProvider, it's not necessary to count size
data from getExternalStorageStats when calculating
size data.
Bug: 185542752
Test: make RunSettingsRoboTests ROBOTEST_FILTER=testMeasurementCompletedUpdatesPreferences
manual
1. Connect device to PC via USB File transfer.
2. Copy large files from PC to device.
3. Observe size information in Storage Settings.
Change-Id: I43cbec764e97f5003a4ec981717c9f213a21b614