ScrollView fails when contentInsetAdjustmentBehavior is automatic

Summary:
Fix to reactwg/react-native-new-architecture#30
We have already applied this solution to both [pre-Fabric](https://www.internalfb.com/code/fbsource/[1da0f2e3164d6f87e8221e0f0462ae93fdc5cbdc]/xplat/js/react-native-github/React/Views/ScrollView/RCTScrollView.m?lines=361) and [Fabric](https://www.internalfb.com/code/fbsource/[1da0f2e3164d6f87e8221e0f0462ae93fdc5cbdc]/xplat/js/react-native-github/React/Fabric/Mounting/ComponentViews/ScrollView/RCTEnhancedScrollView.mm?lines=36) scroll views. However Fabric can reuse components, and this has to be reapplied at every reuse.
Changelog [iOS][Fixed] - ScrollView's contentInsetAdjustmentBehavior is reset to Never at every reuse to avoid layout artifacts.

Reviewed By: cipolleschi

Differential Revision: D35965080

fbshipit-source-id: 3ac26cf304b608d09ae6c0f05588b664381551f2

React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm

@@ -97,6 +97,7 @@ @implementation RCTScrollViewComponentView {
   // This helps to only update state from `scrollViewDidScroll` in case
   // some other part of the system scrolls scroll view.
   BOOL _isUserTriggeredScrolling;
+  BOOL _shouldUpdateContentInsetAdjustmentBehavior;
 
   CGPoint _contentOffsetWhenClipped;
 }
@@ -120,6 +121,7 @@ - (instancetype)initWithFrame:(CGRect)frame
     _scrollView.delaysContentTouches = NO;
     ((RCTEnhancedScrollView *)_scrollView).overridingDelegate = self;
     _isUserTriggeredScrolling = NO;
+    _shouldUpdateContentInsetAdjustmentBehavior = YES;
     [self addSubview:_scrollView];
 
     _containerView = [[UIView alloc] initWithFrame:CGRectZero];
@@ -266,7 +268,8 @@ - (void)updateProps:(Props::Shared const &)props oldProps:(Props::Shared const &
     }
   }
 
-  if (oldScrollViewProps.contentInsetAdjustmentBehavior != newScrollViewProps.contentInsetAdjustmentBehavior) {
+  if ((oldScrollViewProps.contentInsetAdjustmentBehavior != newScrollViewProps.contentInsetAdjustmentBehavior) ||
+      _shouldUpdateContentInsetAdjustmentBehavior) {
     auto const contentInsetAdjustmentBehavior = newScrollViewProps.contentInsetAdjustmentBehavior;
     if (contentInsetAdjustmentBehavior == ContentInsetAdjustmentBehavior::Never) {
       scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
@@ -277,6 +280,7 @@ - (void)updateProps:(Props::Shared const &)props oldProps:(Props::Shared const &
     } else if (contentInsetAdjustmentBehavior == ContentInsetAdjustmentBehavior::Always) {
       scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentAlways;
     }
+    _shouldUpdateContentInsetAdjustmentBehavior = NO;
   }
 
   MAP_SCROLL_VIEW_PROP(disableIntervalMomentum);
@@ -390,6 +394,11 @@ - (void)prepareForRecycle
 {
   const auto &props = *std::static_pointer_cast<const ScrollViewProps>(_props);
   _scrollView.contentOffset = RCTCGPointFromPoint(props.contentOffset);
+  // We set the default behavior to "never" so that iOS
+  // doesn't do weird things to UIScrollView insets automatically
+  // and keeps it as an opt-in behavior.
+  _scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
+  _shouldUpdateContentInsetAdjustmentBehavior = YES;
   _state.reset();
   _isUserTriggeredScrolling = NO;
   [super prepareForRecycle];