Summary:
The PR description has been updated to reflect the new approach.
**Breaking Change Summary**
On Android, the following properties now return a different number:
- `Dimensions.get('window').fontScale`
- `Dimensions.get('screen').fontScale`
- `PixelRatio.getFontScale()`
This is a breaking change to anyone who was using these properties because the meaning of these properties has now changed.
These properties used to return a value representing font scale times density ([`DisplayMetrics.scaledDensity`](https://developer.android.com/reference/android/util/DisplayMetrics.html#scaledDensity)). Now they return a value representing just font scale ([`Configuration.fontScale`](https://developer.android.com/reference/android/content/res/Configuration.html#fontScale)).
**PR Description**
This PR changes a few things:
- Correctly exposes the font scale to JavaScript as `Dimensions.get('screen').fontScale`. UIManager was exporting `DisplayMetrics.scaledDensity` under the name `fontScale`. How
Closes https://github.com/facebook/react-native/pull/11008
Differential Revision: D4558207
Pulled By: astreet
fbshipit-source-id: 096ce7b28051325dfd45fdb2a14b5e9b7d3bc46f
186f308aec