Summary:
Flashing scroll indicators is a standard behavior on iOS to show the user there's more content.
Launch RNTester on iOS, go to the ScrollView section, tap the "Flash scroll indicators" button.
You'll see this:

I've exposed the method `flashScrollIndicators` on all scrolling components that were already exposing a `scrollToXXX` method so it's usable from those components using a ref.
Let me know what you think.
Closes https://github.com/facebook/react-native/pull/14058
Differential Revision: D5103239
Pulled By: shergin
fbshipit-source-id: caad8474fbe475065418d771b17e4ea9766ffcdc
Summary:
When ListViews has multiple sections, then rowIDs are required to be unique per section.
However the ListViewMock required rowIDs to be unique per whole list.
This change fixes the limitation of ListViewMock.
Closes https://github.com/facebook/react-native/pull/13642
Differential Revision: D5189675
Pulled By: shergin
fbshipit-source-id: 8a4fb68feb74af3307407d6d70f3f6642f50452a