Merge "Modify the comment for accessibility_button_mode" into sc-v2-dev am:...

Merge "Modify the comment for accessibility_button_mode" into sc-v2-dev am: 260d9d80 am: 43245736

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15433218

Change-Id: I05c19ec794f71ad458b166b6a6945ec204014a4f