Fix broken HorizontalScrollViewTest

Fixes: 182919494

The stretch effect is more subtle so a drag of 50 pixels
isn't enough to get the stretch effect. Changed to 90 pixels.

Test: ran testStretchAtLeft and testStretchAtRight on cuttlefish
Change-Id: I22ec1a6a46790a8d26ec77d02ff9adecd82e26ff
1 file changed