Package new PDF.js version: v1.0.907

These changes come from the generic build
of PDF.js v1.0.907, with zero changes.

(I'll re-apply our changesin the next few commits.)
Remove unused 1M sample PDF
PDF.js: re-add our 2-liner viewer customizations
Merge pull request #1789 from hypothesis/1778-update-packaged-pdf.js

Chrome extension: update packaged PDF.js code to v1.0.907