Fix rerender count on RNTester blue tab (#22876)
Fix rerender count on RNTester blue tab (#22876)

Summary:
In the RNTester TabBarIOS screen, the content of the blue tab suggested it should be displaying a count for the number of rerenders, but it was not:

![before](https://user-images.githubusercontent.com/15832198/50725270-d122e100-10c0-11e9-88a2-1030f6dc3b9a.jpg)

This PR adds the count onto the blue tab:

![after](https://user-images.githubusercontent.com/15832198/50725275-dbdd7600-10c0-11e9-9f8f-0835fe1ea054.jpg)

The other two tabs already had the counter working correctly.

Changelog:
----------

[General] [Fixed] - Fix rerender count on RNTester blue tab
Pull Request resolved: https://github.com/facebook/react-native/pull/22876

Differential Revision: D13593262

Pulled By: PeteTheHeat

fbshipit-source-id: b45a9fcaed0f217054baa0d28fd3a2ff9a846b08

janicduplessis/react-native,javache/react-native,facebook/react-native,hammerandchisel/react-native,janicduplessis/react-native,hammerandchisel/react-native,exponentjs/react-native,hoangpham95/react-native,pandiaraj44/react-native,janicduplessis/react-native,exponent/react-native,exponent/react-native,facebook/react-native,hoangpham95/react-native,janicduplessis/react-native,facebook/react-native,exponentjs/react-native,hammerandchisel/react-native,hoangpham95/react-native,pandiaraj44/react-native,facebook/react-native,facebook/react-native,exponent/react-native,arthuralee/react-native,arthuralee/react-native,hoangpham95/react-native,myntra/react-native,facebook/react-native,javache/react-native,exponentjs/react-native,arthuralee/react-native,hoangpham95/react-native,hammerandchisel/react-native,exponent/react-native,hammerandchisel/react-native,javache/react-native,exponent/react-native,pandiaraj44/react-native,exponentjs/react-native,myntra/react-native,javache/react-native,exponentjs/react-native,exponentjs/react-native,arthuralee/react-native,arthuralee/react-native,pandiaraj44/react-native,facebook/react-native,javache/react-native,hoangpham95/react-native,facebook/react-native,pandiaraj44/react-native,hoangpham95/react-native,myntra/react-native,myntra/react-native,myntra/react-native,exponent/react-native,myntra/react-native,javache/react-native,myntra/react-native,janicduplessis/react-native,javache/react-native,hammerandchisel/react-native,pandiaraj44/react-native,hammerandchisel/react-native,janicduplessis/react-native,hoangpham95/react-native,exponent/react-native,javache/react-native,janicduplessis/react-native,javache/react-native,exponentjs/react-native,facebook/react-native,pandiaraj44/react-native,janicduplessis/react-native,exponentjs/react-native,hammerandchisel/react-native,myntra/react-native,myntra/react-native,pandiaraj44/react-native,exponent/react-native