No it does not, Firefox still uses PDF.js. This is extremely easy to verify by just right clicking and hitting "Inspect Element" on any PDF opened in Firefox (a

No it does not, Firefox still uses PDF.js. This is extremely easy to verify by just right clicking and hitting "Inspect Element" on any PDF opened in Firefox (and also you can then just load PDF.js into Chrome on a page, load a pdf into that, and verify the same behavior.)