feat(wddebugger): enable repl for browser.pause

No, because JSON.stringify will guarantee it's a proper JSON. 

i.e.
```
> JSON.parse(JSON.stringify({a:3, b:function() {}, c:undefined, d:null}))
{ a: 3, d: null }
> JSON.parse(JSON.stringify([3, undefined]))
[ 3, null, 4 ]
```