Centering a dynamically-sized `titleView` in navigation bar without autolayout

Question

I'm new to iOS layouts, and I'm trying to programmatically centre a custom view (actually a React Native RCTRootView which extends UIView, if that's relevant) which has intrinsically sized, dynamic content (defined over in javascript land).

I've seen solutions overriding intrinsicallySizedContent but that seems to be only relevant to auto-layout, which isn't used by RN. The only way I've been able measure the size of the RCTRootView's content is by adding it to a view, and waiting over several passes of layoutSubViews until its frame has a size. That led me to the following effort:

Attempt: Wrap and set wrapper size in layoutSubViews

I'm wrapping the RCTRootView in another UIView and trying to override layoutSubViews, setting the size of my wrapping frame once I have the size of the react native content.

My wrapper is created and added to the navigation bar in my UIViewController like this:

  RCTBridge *bridge = ((RCTRootView*)self.view).bridge;
  RCTRootView *reactView = [[RCTRootView alloc] initWithBridge:bridge moduleName:navBarCustomView initialProperties:initialProps];
  RCCCustomTitleView *titleView = [[TitleWrapperView alloc] initWithFrame:self.navigationController.navigationBar.bounds subView:reactView];
  self.navigationItem.titleView = titleView;
  self.navigationItem.titleView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin;

And the wrapper is implemented like this:

#import "TitleWrapperView.h"
#import <React/RCTRootView.h>

@interface TitleWrapperView ()
@property (nonatomic, strong) RCTRootView *subView;
@end

@implementation TitleWrapperView // Extends UIView

-(instancetype)initWithFrame:(CGRect)frame subView:(RCTRootView*)subView {
    self = [super initWithFrame:frame];
    
    if (self) {
        self.subView = subView;
        self.subView.sizeFlexibility = RCTRootViewSizeFlexibilityWidthAndHeight;
        self.clipsToBounds = true;

        // Prevent the wrapper from being so large initially as to squash the '< Back' button down to '<'
        self.frame = CGRectZero;

        [self addSubview:subView];
    }
    
    return self;
}

-(void)layoutSubviews {
    [super layoutSubviews];
    CGRect contentViewFrame = self.subView.contentView.frame;
    if (contentViewFrame.size.width > 0) {
        // Once we have a measurement for the sub-view's content, set the wrapper's frame
        if (self.frame.size.width != contentViewFrame.size.width) {
            self.frame = contentViewFrame;
        }
    }
}
@end

That works a treat on iOS 11+, but not on iOS 10.3, where when the screen containing the custom nav (the red box) is pushed, the navigation transition animates the titleView over towards the top left, rather than into the centre (the end position, which is correct) as I'd hope:

Other approaches?

There might be a way to overcome the iOS 10 glitch above (and I'd love to hear it) but I'm fairly certain there must be a better approach. Is is possible to allow an arbitrary, complex view to lay itself out and get its measurement before adding it to a parent? I've also tried overriding sizeThatFits in my wrapper, which is called by the navigation bar, and requesting the size of my RCTRootView using [subView sizeThatFits: myLargeContainer], but I get 0,0 back.

I'm at a loss - any pointers are appreciated.