Add GrOpList and rename GrDrawTarget to GrRenderTargetOpList

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3910

Change-Id: I026aa26ecc61a0d002e98892dca728536259e8b1
Reviewed-on: https://skia-review.googlesource.com/3910
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/include/gpu/GrGpuResource.h b/include/gpu/GrGpuResource.h
index 364a886..d3cfa86 100644
--- a/include/gpu/GrGpuResource.h
+++ b/include/gpu/GrGpuResource.h
@@ -23,7 +23,7 @@
  *
  * Gpu resources can have three types of refs:
  *   1) Normal ref (+ by ref(), - by unref()): These are used by code that is issuing draw calls
- *      that read and write the resource via GrDrawTarget and by any object that must own a
+ *      that read and write the resource via GrOpList and by any object that must own a
  *      GrGpuResource and is itself owned (directly or indirectly) by Skia-client code.
  *   2) Pending read (+ by addPendingRead(), - by completedRead()): GrContext has scheduled a read
  *      of the resource by the GPU as a result of a skia API call but hasn't executed it yet.