这个组件是在0.46.4新加入的一个组件，加入该组件的原因
https://github.com/facebook/react-native/commit/9637dd4a1b78d5f6da510b1b4ad10d45d67badbf
注意：该组件还未真正上完全实现下面的目的
Summary: We are removing support of nesting views inside <Image> component. We decided to do this because having this feature makes supporting `intrinsinc content size` of the `<Image>` impossible; so when the transition process is complete, there will be no need to specify image size explicitly, it can be inferred from actual image bitmap. And this is the step #0. <ImageBackground> is very simple drop-in replacement which implements this functionality via very simple styling. Please, use <ImageBackground> instead of <Image> if you want to put something inside.