[base] Update GrDirectContext calls to use safer API

In http://review.skia.org/750403 and http://review.skia.org/751523,
Skia modified some GrDirectContext APIs to make them less error-prone
in response to https://crbug.com/1475906.

This updates part of Android to call those modified APIs.

Change-Id: I164fcc735b3c36bf58de2f1ed9f277e90fc09325