Revert "Add notion of active opList to GrDrawingManager"

This reverts commit 328f9c72ee9a5ffe76f886bd83b17f50ef7a573c.

Reason for revert: assert is breaking Chrome roll

Original change's description:
> Add notion of active opList to GrDrawingManager
> 
> With an incrementally sorted list of opLists we will no longer be able to
> assume that the last opList is the active one.
> 
> This is pulled out of: https://skia-review.googlesource.com/c/skia/+/150614 (Begin centralizing opList DAG) and also contains some of the non-substantive changes from that CL.
> 
> Change-Id: Ic3d264565afa61b19e2125c38a6ad053292bc7d9
> Reviewed-on: https://skia-review.googlesource.com/151021
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Robert Phillips <robertphillips@google.com>

TBR=bsalomon@google.com,robertphillips@google.com

Change-Id: I01647301a59e21da8dd1ad2aa4652cfc52b095ea
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/151369
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
2 files changed