Make initBatchTracker private, move towards pipeline on batch

src/gpu/GrTargetCommands.h

Index: src/gpu/GrTargetCommands.h
diff --git a/src/gpu/GrTargetCommands.h b/src/gpu/GrTargetCommands.h
index 4de75897fcb5f523968ab6a986890b8ac8a78721..f5f0004d079638324e3da966089c8d67a012e808 100644
--- a/src/gpu/GrTargetCommands.h
+++ b/src/gpu/GrTargetCommands.h
@@ -241,7 +241,7 @@ private:
     };
 
     struct DrawBatch : public Cmd {
-        DrawBatch(State* state, GrBatch* batch, GrBatchTarget* batchTarget)
+        DrawBatch(const State* state, GrBatch* batch, GrBatchTarget* batchTarget)
             : Cmd(kDrawBatch_CmdType)
             , fState(SkRef(state))
             , fBatch(SkRef(batch))
@@ -251,8 +251,8 @@ private:
 
         void execute(GrGpu*) override;
 
-        SkAutoTUnref<State>    fState;
-        SkAutoTUnref<GrBatch>  fBatch;
+        SkAutoTUnref<const State>   fState;
+        SkAutoTUnref<GrBatch>       fBatch;
 
     private:
         GrBatchTarget*         fBatchTarget;