Fix DDL reattachment of uniquely keyed proxies

This fix has three parts:
   No longer clear all proxy unique keys in DDL mode
   Handle unique keys appropriately in lazy proxy instantiation
   Handle attaching to cached surfaces for non-lazy proxies

Change-Id: I86b0422a784acaf8c5f9b67cb981b440e08352de
Reviewed-on: https://skia-review.googlesource.com/154502
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
8 files changed