This only affects the printing of web pages directly on the host.

- Renderer tells the browser if the print job is HTML. (AKA modifiable)
-- Browser does lots of plumbing to get the bool into PrintSettings.
-- Print preview already sends this info and it just needs extraction.
- Add --disable-gdi-text-printing for reverting to old behavior.
- Browser plumbs bool to PdfToEmfConverter to the utility process.
- Utility plumbs bool into the PDF plugin code into PDFium.
- Move unused PreCacheFontCharacters code out of RenderThreadImpl.
-- Use it in PrintingHandler instead.
- Remove dead code, fix lint errors / typos.

BUG=409472

Review-Url: https://codereview.chromium.org/2114583002
Cr-Commit-Position: refs/heads/master@{#414209}