Enable range requests in Safari (both OSX and IOS)

Attach (recommended) or Link to PDF file here: https://mozilla.github.io/pdf.js/web/compressed.tracemonkey-pldi-09.pdf

Configuration:

• Web browser and its version: Safari 11.1 (OSX), Safari 11.0 (IOS)
• Operating system and its version: OSX 10.13.4, IOS 11.4
• PDF.js version: latest from master
• Is a browser extension: no

Steps to reproduce the problem:

1. Start dev server with gulp server
2. Visit http://localhost:8888/web/viewer.html
3. Observe network tab for 206 requests

What is the expected behavior? (add screenshot) The document is loaded using range requests

What went wrong? (add screenshot) The document is loaded with a single request. It looks like range requests were explicitly disabled by this code here:

  // Support: Safari 6.0+, iOS
  (function checkRangeRequests() {
    // Safari has issues with cached range requests, see issue #3260.
    // Last tested with version 6.0.4.
    if (isSafari || isIOS) {
      compatibilityParams.disableRange = true;
      compatibilityParams.disableStream = true;
    }
  })(); 

It feels a bit outdated. I’ve just tested pdfjs without this code in the specified browsers and it worked just fine. Is there a reason for keeping this code?

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

[timvandermeij]

@fooware Thank you for looking into this. Given that range requests work again since Safari 9, I think we can remove the compatibility check because Safari 9 is the minimum version we support.

@yurydelendik @Snuffleupagus I have updated https://github.com/mozilla/pdf.js/wiki/Frequently-Asked-Questions#which-browsers-are-supported to reflect that we only support iOS 10 and higher for Safari, as decided above. When I made the overview there, I looked through the commits we did for version 2.0 and found a commit where polyfills were removed that stated that Safari 8+ was now the minimum, but I can’t find it quickly anymore. However, since Safari 8 is almost three years old, I think we can safely drop explicity support for it, so I updated the page to reflect this too. I think it’s a fair support we have now.

If someone wants to create a patch to remove the compatibility code, please also bump https://github.com/mozilla/pdf.js/blob/620da6f4df6eb883ff89580b643ef0516035e0d0/gulpfile.js#L81 to >= 9.

[timvandermeij]

Not really, and we would like to limit it where possible. Could you indicate from which Safari/iOS versions range request work again, since it was apparently broken before?