Use enabled scrolling child in BottomSheetBehavior

Modification of findScrollingChild() that only returns a view if
it has nested scrolling enabled (instead of just implementing
NestedScrollingChild). As to prevent an incorrect view being
referrenced, leading to incorrect behavior when scrolling.

Test: added BottomSheetBehaviorTest.testFindScrollingChildEnabled()
that tests that an enabled NestedScrollView contained within a disabled
NestedScrollView parent is returned by findScrollingChild(parent)

Change-Id: I9841db9c67520f858913a5109dc08ffed9e53568
2 files changed