Revert "Add a new GrResourceCache purging mechanism for purging unused resources."

This reverts commit fbb56ce83fc717b7c6722324bbccd1ae73c350a4.

Reason for revert: Chrome's ancient libstdc++ doesn't like use of steady_clock

Original change's description:
> Add a new GrResourceCache purging mechanism for purging unused resources.
> 
> The client may call GrContext::purgeResourceNotUsedSince() with a stead_clock::time_point and all resources that have been purgeable since before that time point are purged.
> 
> This is intended to replace the "max unused flushes" purging mechanism once Chrome adopts it.
> 
> Change-Id: I28881dd2959cc01c0acca81b2d6001ee5626439d
> Reviewed-on: https://skia-review.googlesource.com/8920
> Commit-Queue: Brian Salomon <bsalomon@google.com>
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Reviewed-by: Eric Karl <ericrk@google.com>
> 

TBR=bsalomon@google.com,robertphillips@google.com,ericrk@google.com,reviews@skia.org,ericrk@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I3baa3b2e80302315b757d4d625732459e13795d4
Reviewed-on: https://skia-review.googlesource.com/10004
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
7 files changed