Replace websocket for navigate/resource differentiation

[jakearchibald]

Instead use: http://developer.chrome.com/extensions/webRequest.html

'onbeforerequest' to sync add "for-service-worker" header

The event has a type http://developer.chrome.com/extensions/webRequest.html#property-details-type

Which is:

• "main_frame" for navigate where isTopLevel is true
• "sub_frame" for navigate where isTopLevel is false
• Everything else is resource

[tgvashworth]

Fixed in bb95d28