Investigate upgrading Gulp, Webpack and Node.js dependencies

[timvandermeij]

From #10176:

Webpack is pinned because versions higher than this cause the viewer not
to work (see https://github.com/mozilla/pdf.js/pull/10170#issuecomment-431697032).

Node.js is pinned for Travis CI because version 11 requires that we
update to Gulp 4.

[Snuffleupagus]

Webpack is pinned because versions higher than this cause the viewer not to work (see #10170 (comment)).

The problem is that Webpack, starting from version 4.22.0, is now parsing the entire

typeof __non_webpack_require__ !== 'undefined'

expression during the build process, causing the above line to be reduced to true.
The expected, and previous output, is that __non_webpack_require__ is replaced with require as

typeof require !== 'undefined'

According to the documentation, this should still work; see https://webpack.js.org/api/module-variables/#__non_webpack_require__-webpack-specific-

If someone has time (since a reduced test-case might be needed), this should be reported to https://github.com/webpack/webpack/issues

[timvandermeij]

Gulp and Node.js are taken care of in the meantime, only Webpack remains.

[Snuffleupagus]

Was the Webpack regression described in #10177 (comment) ever reported upstream, or has it perhaps already been fixed in a later release?

(You could probably hack around this on the PDF.js side, by using e.g. PDFJSDev.eval or similar, but that would IMHO be a last resort if the Webpack regression isn't fixed.)

[timvandermeij]

I tried the latest release last time I updated the dependencies and it isn't fixed yet, nor do I really know how to report this in a way that it's actionable for upstream because I don't know that much about this part of the codebase to reduce it to a minimal example.

[timvandermeij]

I have filed an upstream issue for this bug at webpack/webpack#8829. If that is fixed, we can remove the workaround. Tracking this upstream now.