Measure touch events from nearest "root view"
Measure touch events from nearest "root view"

Summary:
This makes RCTTouchHandler follow the same logic when sending touch event
coordinates as `UIManager.measure`.
This is important as UIManager.measure is used in `Touchable.js` aka the mother
of all touch events in RN.

In particular, this will make touch events correctly handled for places where RN is embedded into other screens.

Reviewed By: shergin

Differential Revision: D6838102

fbshipit-source-id: 70cad52606ea931cb637d8aa2d4845818eea0647

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