Properly animate reactions without jitter [IG Direct] [Reactions Emitter Animation] [7/x]

Summary: We add a boolean isDisplayingCell method to check the existence of displayingCell in IGListBindingSingleSectionController

Reviewed By: chritto

Differential Revision: D20649871

fbshipit-source-id: f626cfdedff907604514c485d11362cd9ba12b99

Source/IGListKit/IGListBindingSingleSectionController.h

@@ -46,6 +46,8 @@ NS_SWIFT_NAME(ListBindingSingleSectionController)
 // Subclasable. Defaults is no-op.0
 - (void)didUnhighlightItemWithCell:(Cell)cell;
 
+- (BOOL)isDisplayingCell;
+
 @end
 
 NS_ASSUME_NONNULL_END

Source/IGListKit/IGListBindingSingleSectionController.m

@@ -116,4 +116,8 @@
     [super didEndDisplayingCell:cell atIndex:index listAdapter:listAdapter];
 }
 
+- (BOOL)isDisplayingCell {
+    return _displayingCell != nil;
+}
+
 @end