SkPDF: skia_pdf_less_compression - for debugging only

SkPDF: skia_pdf_less_compression - for debugging only

Motivation: as we implement more features in PDF, it would be nice to more easily see what is happening in the output.  This change serializes page content as plain text rather than compressed text, but it has to be explicitly enabled with a GYP_DEFINE change:

    export GYP_DEFINES='skia_pdf_less_compression=1'
    bin/sync-and-gyp
    ninja -C out/Debug dm
    out/Debug/dm --config pdf --src gm -w /tmp

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1840103002

Review URL: https://codereview.chromium.org/1840103002