Just an experiment

src/gpu/GrDrawTarget.h

Index: src/gpu/GrDrawTarget.h
diff --git a/src/gpu/GrDrawTarget.h b/src/gpu/GrDrawTarget.h
index b12ac99de4504c5766ef0f38c26d6a5d1f32224d..81dc7e6cb0cd15976c5c8993922aa8c83b62dd77 100644
--- a/src/gpu/GrDrawTarget.h
+++ b/src/gpu/GrDrawTarget.h
@@ -200,6 +200,14 @@ public:
 
     const CMMAccess cmmAccess() { return CMMAccess(this); }
 
+    GrBatch* lastBatch() {
+        if (fBatches.count()) {
+            return fBatches.back();
+        } else {
+            return nullptr;
+        }
+    }
+
 private:
     void recordBatch(GrBatch*);
     bool installPipelineInDrawBatch(const GrPipelineBuilder* pipelineBuilder,