Summary:
Now things look much more clear, I hope.
This diff:
* Introduces new property of `RCTRootShadowView` `availableSize` which represents exactly what we transmit to layout engine;
* Illuminates conflict between logical `availableSize` and explicitly specified size of DOM node (current `size`);
* Splits overcomplicated `setSize:forView:` method into two unrelated ones;
* Changes actual values of `RCTRootViewSizeFlexibility` enum constants for simpler usage;
* Completely removes `sizeFlexibility` concept from `RCTRootShadowView` (in favor of special values of `availableSize`);
* Makes the code clearer finally.
This is beginning of big effort to improve `RCTRootView` and co.
Reviewed By: mmmulani
Differential Revision: D4562834
fbshipit-source-id: f5baaf2859ea430d44645a6b5d35f222f15a668e
ba170ec78c