b/428824494
b/428649314

Run the https://github.com/flutter/flutter/tree/master/dev/a11y_assessments and navigate to Navigation rail

b/428819909
b/428716579
Slider in slider sample

EXPECTED RESULTS:

VoiceOver announces "[accessibilityLabel], 20, 20 percent, adjustable, Swipe up or down with one finger to adjust the value" or similar.

b/428643704
next button in app bar demo

alkBack announces " Go to the next page, Button,...."