This patch:
- resolves a warning in the console about missing character encoding;
- makes the viewer use the same background color and PDF file as the
regular viewer;
- simplifies the example to bring it more in line with the other
examples.
Re: issue 7017.
This should prevent the error, but does not fix the broken rendering.
The rendering issues are caused by `svg.js` not supporting the various text rendering modes, in this case specifically "invisible" (as indicated in the console `Warning: Unimplemented method setTextRenderingMode`).
Compared to the canvas case, where we just ignore invisible text, a smarter solution is probably required for the SVG case. Since just ignoring invisible text in `svg.js` would mean that text-selection isn't possible.
