Follow up from https://github.com/facebook/react/pull/11616.

Here's one I found. These two invariants:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L330-L343

are in a function that's behind a DEV block:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L447-L449

I don't think this is intentional, but need to verify.

There may be more. I'll use this issue to track while https://github.com/facebook/react/pull/11616 preserves existing behavior.
var contextTypes = type.contextTypes;
  if (!contextTypes) {
    return emptyObject;
  }
  var maskedContext = {};
  for (var contextName in contextTypes) {
    maskedContext[contextName] = context[contextName];
  }
  return maskedContext;
}
function checkContextTypes(typeSpecs, values, location: string) {
  if (__DEV__) {
    checkPropTypes(typeSpecs, values, location, 'Component', getStackAddendum);
  }
}
function processContext(type, context) {