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

This reverts commit 742f3d02a1c6a916d7e0ed3bedb0b546bbe3c15f.

Reason for revert: Aaah!

Original change's description:
> Make threaded proxy generation MDB-friendly, and defer instantiation
> 
> Replaces GrPrepareCallback with GrDeferredProxyUploader, stored directly
> on GrTextureProxy. Op lists now store a list of referenced proxies that
> are being generated by worker threads. At flush time, iterate over those
> proxies, and invoke their uploader.
> 
> Lifetime of the uploader object is now tied to the proxy, but the ASAP
> upload function will free the proxy's uploader, if it's called.
> 
> Bug: skia:
> Change-Id: Ieb2c6a805d19990012839a8e103c3ca5b8d3dfc6
> Reviewed-on: https://skia-review.googlesource.com/49904
> Commit-Queue: Brian Osman <brianosman@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>

TBR=egdaniel@google.com,robertphillips@google.com,brianosman@google.com

Change-Id: I8f76a67044dc4159f903097d8b1ef19ffb48c730
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/52760
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
11 files changed