Make all GrRenderTargetOpList ops store a GrRenderTarget pointer

Change-Id: I39652b4b8b2ba96b5206304dfc51395283c3fe16
Reviewed-on: https://skia-review.googlesource.com/13332
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/ops/GrOp.h b/src/gpu/ops/GrOp.h
index ef752b5..7f8f8e7 100644
--- a/src/gpu/ops/GrOp.h
+++ b/src/gpu/ops/GrOp.h
@@ -151,6 +151,8 @@
         return string;
     }
 
+    virtual bool needsCommandBufferIsolation() const { return false; }
+
 protected:
     /**
      * Indicates that the op will produce geometry that extends beyond its bounds for the