Re: [fetch] Initializing context/content specific fetch defaults (#43)

@annevk after doing a quick spot-check, the advertised Accept headers are all over the map...

#### Chrome...
Type  | Header
------- | -------------
HTML | `text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8`
JS | `*/*`
CSS | `text/css,*/*;q=0.1`
Image | `image/webp,*/*;q=0.8`
Video | `*/*`

#### Firefox
Type  | Header
------- | -------------
HTML | `text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8`
JS |  `*/*`
CSS | `text/css,*/*;q=0.1`
Image | `image/png,image/*;q=0.8,*/*;q=0.5`
Video | `video/webm,video/ogg,video/*;q=0.9,application/ogg;q=0.7,audio/*;q=0.6,*/*;q=0.5`

#### Safari
Type  | Header
------- | -------------
HTML | `text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8`
JS  | `*/*`
CSS | `text/css,*/*;q=0.1`
Image | `*/*`
Video | `*/*`

#### IE
Type  | Header
------- | -------------
HTML | `text/html, application/xhtml+xml, */*`
JS  | `application/javascript, */*;q=0.8`
CSS | `text/css, */*`
Image | `image/png, image/svg+xml, image/*;q=0.8, */*;q=0.5`
Video | `*/*`

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I guess one way to look at this would be to say that perhaps Fetch is the one place where we can (finally) rationalize and normalize all this across the different browsers? However, even if we were to go down that route, we still need to allow for UA-specific values (e.g. WebP advertisements for Chrome, and so on). As a result, perhaps a fixed list of `context -> Accept headers` within fetch spec is also not the best route? Should we keep it more general? Same applies for prioritization...

/cc @mnot 


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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/43#issuecomment-97909717