Allow aliasing in GrProxyProvider::processInvalidUniqueKey

Rearranges the code to support the case "&key == &proxy->fUniqueKey".
Removes the redundant GrUniqueKey parameter from
GrProxyProvider::removeUniqueKeyFromProxy (we can just get the key
from the proxy itself). Adds a passthru for "processInvalidUniqueKey"
to GrOnFlushResourceProvier.

Bug: skia:8462
Change-Id: I0c1e1f2c6ff15a9976f8475c19fd8a33a363193c
Reviewed-on: https://skia-review.googlesource.com/c/180048
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
9 files changed