Add Sharing Histories to UsageStatsManager.

This CL is for Android O Smart-Sharing (b/30982298). By this CL, sharing
counts are logged with UsageStatsManager.

Bug: 30982298
Test: manual - shared images in Camera and texts in Chrome using a mobile device.

Change-Id: I0b4aa0506f99b3083d140a48f7b4bdd5b1c5afb6