[fetch] Should Headers(undefined) throw? (#185)

On reading the spec I'm not clear if this is a bug in Chrome or not
```
new Headers(undefined)
VM440:2 Uncaught TypeError: Failed to construct 'Headers': No matching constructor signature.(…)(anonymous function) @ VM440:2InjectedScript._evaluateOn @ VM363:875InjectedScript._evaluateAndWrap @ VM363:808InjectedScript.evaluate @ VM363:664
new Headers()
Headers {}
```

The spec says 

> The Headers(init) constructor, when invoked ... If init is given, fill headers with init. 

Before I raise a Chrome bug could someone clarify if the above behaviour is compliant with the spec. Should passing `undefined` to `Headers()` qualify as 'init is given'? 


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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/185