UserAgent: Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.87 Safari/537.36

Steps to reproduce the problem:
See [this jsbin](http://jsbin.com/seridu/edit?js,console,output

```
function* sayThrice(val = {}) {
	let cntr = 1;
	console.log(`${cntr++} - ${val.msg}`)
	yield
	console.log(`${cntr++} - ${val.msg}`)
	yield
	console.log(`${cntr++} - ${val.msg}`)
}

const runIt = it => {
	while(!it.next().done) {}
}

runIt(
	sayThrice({msg: "hi there"})
)
```

Running the above with devtools open crashes the browser. 

It works fine without devtools open.

It works fine if I *don't* use a default parameter and default it in the old-school way `val || (val = {})`

What is the expected behavior?
For everything not to crash and die a horrible death

What went wrong?
Seems like some sort of infinite loop that triggers when generators and default parameters work in conjunction

Did this work before? No 

Chrome version: 49.0.2623.87  Channel: stable
OS Version: 10
Flash Version: Shockwave Flash 21.0 r0

Didn't work because we didn't have default parameters before now.