Fix DatePicker sizing issue

Summary:
Changelog: Fix possible sizing issue with DatePicker

Changing `preferredDatePickerStyle` changes size of the component without triggering re-layout of the react native screen. The fix is to make sure the size stays the same after changing the style.

Reviewed By: mdvacca

Differential Revision: D28035226

fbshipit-source-id: 2dcb50fd5ebaa0c0d01d3289c4ffa77a053cfc4a

Author: sammy-SC

React/Views/RCTDatePickerManager.m

@@ -85,11 +85,17 @@ - (UIView *)view
 RCT_CUSTOM_VIEW_PROPERTY(pickerStyle, UIDatePickerStyle, RCTDatePicker)
 {
   if (@available(iOS 14, *)) {
+    // If the style changed, then the date picker may need to be resized and will generate a layout pass to display
+    // correctly. We need to prevent that to get consistent layout. That's why we memorise the old frame and set it
+    // after style is changed.
+    CGRect oldFrame = view.frame;
     if (json) {
-      view.preferredDatePickerStyle = [RCTConvert UIDatePickerStyle:json];
+      UIDatePickerStyle style = [RCTConvert UIDatePickerStyle:json];
+      view.preferredDatePickerStyle = style;
     } else {
       view.preferredDatePickerStyle = UIDatePickerStyleWheels;
     }
+    view.frame = oldFrame;
   }
 }
 #endif