SkPDF: refactor generate_page_tree

function now takes a constant ref, as needed.

re-written to make it easier to think about state.

Change-Id: I5b9935cd88b4f8b1f35d4df622adcfb61655d42b
Reviewed-on: https://skia-review.googlesource.com/c/160383
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
1 file changed