dillon1000/react

Stop shrinking HIR to preserve fallthrough nodes

This is part of a stack to fix some edge cases in inlining of useMemo closures. 
In this first step, I'm disabling `shrink()` in order to retain more information 
about the data flow. For example, 

``` 

label: if (cond) { 

break label; 

} 

return foo; 

``` 

Would previously have shrunk away the if body, making the IfTerminal.consequent 
point directly to the fallthrough block (w the return). Now we retain a separate 
block.