For proof-of-concept, this patch converts a couple of `Promise` returning methods to use `async` instead.
Please note that the `generic` build, based on this patch, has been successfully testing in IE11 (i.e. the viewer loads and nothing is obviously broken).
Being able to use modern JavaScript features like `async`/`await` is a huge plus, but there's one (obvious) side-effect: The size of the built files will increase slightly (unless `SKIP_BABEL == true`). That's unavoidable, but seems like a small price to pay in the grand scheme of things.
Finally, note that the `chromium` build target was changed to no longer skip Babel translation, since the Chrome extension still supports version `49` of the browser (where native `async` support isn't available).
The various classes have `this._errored` and `this._reason` properties, where the first one is a boolean indicating if an error was encountered and the second one contains the actual `Error` (or `null` initially).
In practice this means that errors are basically tracked *twice*, rather than just once. This kind of double-bookkeeping is generally a bad idea, since it's quite easy for the properties to (accidentally) get into an inconsistent state whenever the relevant code is modified.
Rather than using a separate boolean, we can just as well check the "error" property directly (since `null` is falsy).
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Somewhat unrelated to this patch, but `src/display/node_stream.js` is currently *not* handling errors in a consistent or even correct way; compared with `src/display/network.js` and `src/display/fetch_stream.js`.
Obviously using the `createResponseStatusError` utility function, from `src/display/network_utils.js`, might not make much sense in a Node.js environment. However at the *very* least it seems that `MissingPDFException`, or `UnknownErrorException` when one cannot tell that the PDF file is "missing", should be manually thrown.
As is, the API (i.e. `getDocument`) is not returning the *expected* errors when loading fails in Node.js environments (as evident from the `pending` API unit-test).
First of all, note how in both `fetch_stream.js` and `node_stream.js` we always overwrite the `this._contentLength` property even when the response headers doesn't actually contain any (valid) length information. This could thus result in the `length` parameter, as passed to the network stream, being completely ignored despite having no better information available.
Secondly, in `node_stream.js` the `this._isRangeSupported` property wasn't always updated correctly based on the response headers.
This patch updates the `IPDFStreamReader` interface and ensures that the interface/implementation of `network.js`, `fetch_stream.js`, `node_stream.js`, and `transport_stream.js` all match properly.
The unit-tests are also adjusted, to more closely replicate the actual behaviour of the various actual `IPDFStreamReader` implementations.
Finally, this patch adjusts the use of the Content-Disposition filename when setting the title in the viewer, and adds `PDFDocumentProperties` support as well.
*This patch is the result of me starting to look into moving parameters from `PDFJS` into `getDocument` and other API methods.*
When familiarizing myself with the code, the signatures of the various network streams seemed to be unnecessarily cumbersome since `disableRange` is currently handled separately from other parameters.
I'm assuming that the explanation for this is probably "for historical reasons", as is often the case. Hence I'd like to clean this up *before* we start the larger, and more invasive, `PDFJS` parameter re-factoring.
