Revert "Revert "Make threaded proxy generation MDB-friendly, and defer instantiation""

This reverts commit 837c6c7c0cc76bdb9d61a05244ca5f31e7573c37.

Bug: skia:
Change-Id: I1821f1b2b772c67f1b749692b398eb757d8073c9
Reviewed-on: https://skia-review.googlesource.com/52744
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
12 files changed