Implement progressive pdf download

[libreliodev]

When we try to download http://librelio-europe.s3.amazonaws.com/librelio/wind/wind_355/wind_355.pdf in Firefox, progressive download works.
When using our PDF reader with the same file (Wind 355) , progressive download does not work.

[AlirezaAlgo]

@libreliodev Firefox pdf reader does not care about CORS setting of your s3 bucket.
You should change CORS setting. Look at my comments in #44

[libreliodev]

@serverfire Thank you for your comment.

As mentioned in #44 , CORS is already in place on this bucket. In order to understand which authorizations are potentially missing, do you have an error message in javascript?

[libreliodev]

@serverfire Could this help: http://stackoverflow.com/questions/15561508/xmlhttprequest-206-partial-content

[libreliodev]

This might also help: mozilla/pdf.js#3150

[libreliodev]

For some reason, this now works under Firefox and Chrome, but not Safari.
Will need to test under IE.

[AlirezaAlgo]

@libreliodev I saw that. It's mostly likely because of CORS setting or the browser does not allow that.
Now i see this response in header.
Access-Control-Expose-Headers: Accept-Ranges, Content-Encoding, Content-Length, Content-Range
It means ajax request can use these request headers. Maybe if you set * is allowed. It will fix safari problem.

[libreliodev]

@serverfire: thanks for the suggestion. However, it's not possible to do this in AWS

ExposeHeader "*" contains wildcard. We currently do not support wildcard for ExposeHeader.

Any idea of the missing header(s)?

[AlirezaAlgo]

I think that's enough. I should see if safari supports partial requests via ajax.

[AlirezaAlgo]

@libreliodev Now safari also requests for pdf file partially.

[libreliodev]

@serverfire Fantastic. Many thanks.