Rename `buttonSize` to `buttonPreferenceSize`.

The name `buttonSize` causes aapt to have a resource merge conflict
with play-services-base when compiling in gradle. Changing the
name avoids the conflict.

Fixes: 370558301
Test: test_gradle_build.sh
Flag: EXEMPT minor refactor
Change-Id: I5d42abe046a177472a6243e172525f247be9e1e8
3 files changed