Don't send events when clicking on scrollbars (#1281)

This will ignore "touches" (clicks) on `NSScroller` such that JS does not process them resulting in a press event.

Confirmed clicking scrollbar in rn-tester does not result in a click on the items underneath.

Co-authored-by: Scott Kyle <skyle@fb.com>

React/Base/RCTTouchHandler.m

@@ -129,6 +129,10 @@ - (void)_recordNewTouches:(NSSet *)touches
     // The assumption here is that a RCTUIView/RCTSurfaceView will always have a superview.
     CGPoint touchLocation = [self.view.superview convertPoint:touch.locationInWindow fromView:nil];
     NSView *targetView = [self.view hitTest:touchLocation];
+    // Don't record clicks on scrollbars.
+    if ([targetView isKindOfClass:[NSScroller class]]) {
+      continue;
+    }
     // Pair the mouse down events with mouse up events so our _nativeTouches cache doesn't get stale
     if ([targetView isKindOfClass:[NSControl class]]) {
       _shouldSendMouseUpOnSystemBehalf = [(NSControl*)targetView isEnabled];
@@ -395,6 +399,11 @@ - (void)interactionsBegan:(NSSet *)touches  // TODO(macOS GH#774)
   // "end"/"cancel" needs to remove the touch *after* extracting the event.
   [self _recordNewTouches:touches];
 
+  // [TODO(macOS GH#774) - Filter out touches that were ignored.
+  touches = [touches objectsPassingTest:^(id touch, BOOL *stop) {
+    return [_nativeTouches containsObject:touch];
+  }]; // ]TODO(macOS GH#774)
+
   [self _updateAndDispatchTouches:touches eventName:@"touchStart"];
 
   if (self.state == UIGestureRecognizerStatePossible) {