[fix] Fixing overscrolling issue on Virtualized List

[dusave]

Changelog:

[iOS][fixed] Fixed overscroll behavior on iOS virtualized lists (Fixes #18098)

Test Plan:

• Create a section list (for iOS)
• Attempt to scroll to an item towards the bottom

Expected: List scrolls to the item to the correct position without overscrolling the list
Actual: List is over scrolling to put the item in the proper position. This causes future scrolling to jump.

Code Used to Test:

this.listRef.scrollToLocation({ animated: true, sectionIndex: 11, itemIndex: 0, viewPosition: 0});

...

<SectionList
  ref={ (ref) => this.listRef = ref }
  renderItem={({item, index, section}) => (
    <Text key={index} style={{flex: 1, padding: 4}}>{item}</Text>
  )}
  renderSectionHeader={({section: {title}}) => (
    <Text style={{flex: 1, padding: 4}}>{title}</Text>
  )}
   sections={[
    {title: 'A', data: ['item1', 'item2']},
    {title: 'B', data: ['item3', 'item4']},
    {title: 'C', data: ['item5', 'item6']},
    {title: 'D', data: ['item1', 'item2']},
    {title: 'E', data: ['item3', 'item4']},
    {title: 'F', data: ['item5', 'item6']},
    {title: 'G', data: ['item1', 'item2']},
    {title: 'H', data: ['item3', 'item4']},
    {title: 'I', data: ['item5', 'item6']},
    {title: 'J', data: ['item1', 'item2']},
    {title: 'K', data: ['item3', 'item4']},
    {title: 'L', data: ['item5', 'item6']},
]}/>

Before:

After:

[pull-bot]

	Warnings
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[cpojer]

Thanks for sending a PR :)

[facebook-github-bot]

@cpojer is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[react-native-bot]

Dustin Savery merged commit 4d5f85e into facebook:master.

[cpojer]

It was pointed out to me that this was not the correct fix for this issue. You should be able to use overScrollMode="never" to fix this problem instead.