+++ This bug was initially created as a clone of Bug #1380899 +++ Changes since last update: #8609 Ensure that `PDFFindBar._adjustWidth` is called in all situations where the width of the findbar might have changed #8634 Update inconsistent names #8618 Remove the scale-not-initialized hack from `webViewerResize` (in app.js) #8641 Update ESLint (and eslint-plugin-mozilla) to the latest version #8620 Improve compression of PNG images embedded in generated SVG files #8649 Convert `PDFLinkService` to an ES6 class #8651 Fix display_svg_spec tests. #8636 Convert `PDFViewer` to an ES6 class #8653 Add UI for the cursorToolOnLoad pref in the Chrome extension + migration logic

Pushed by ryanvm@gmail.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/19aa0ec75020 Update pdf.js to version 1.8.557. r=bdahl