Bug 1017328 - [Flatfish] PDF files render incorrectly in the browser app

* Update pdf.js to version 1.0.524
Bug 1017328 - [Flatfish] PDF files render incorrectly in the browser app

* Update pdf.js to version 1.0.700 to use the new web component based header (gaia-header)
Merge pull request #22397 from begeeben/1017328_pdf_files_render

Bug 1017328 - [Flatfish] PDF files render incorrectly in the browser app, r=yurydelendik

* Update pdf.js to version 1.0.700 to use the new web component based header (gaia-header)