Cancel touches if surface touch handler can be prevented

Summary:
Changelog: [internal]

If `otherGestureRecognizer` prevents Fabric's gesture recogniser, we need to manually reset the inner state.
This cancels any currently active touches.

Reviewed By: shergin

Differential Revision: D25664384

fbshipit-source-id: 9e3cd41351381bcfed2836dad3e80d5f021f936c

React/Fabric/RCTSurfaceTouchHandler.mm

@@ -410,4 +410,14 @@ RCT_NOT_IMPLEMENTED(-(instancetype)initWithTarget : (id)target action : (SEL)act
   return [self canBePreventedByGestureRecognizer:otherGestureRecognizer];
 }
 
+- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
+    shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
+{
+  BOOL canBePrevented = [self canBePreventedByGestureRecognizer:otherGestureRecognizer];
+  if (canBePrevented) {
+    [self reset];
+  }
+  return NO;
+}
+
 @end