Add option to control maximum GrBatch lookback

src/gpu/GrDrawTarget.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDrawTarget_DEFINED
 #define GrDrawTarget_DEFINED
 
@@ skipping 26 matching lines @@
 class GrBatch;
 class GrClip;
 class GrCaps;
 class GrPath;
 class GrDrawPathBatchBase;
 
 class GrDrawTarget final : public SkRefCnt {
 public:
     /** Options for GrDrawTarget behavior. */
     struct Options {
-        Options () : fClipBatchToBounds(false), fDrawBatchBounds(false) {}
+        Options () : fClipBatchToBounds(false), fDrawBatchBounds(false), fMaxBatchLookback(-1) {}
         bool fClipBatchToBounds;
         bool fDrawBatchBounds;
+        int  fMaxBatchLookback;
     };
 
     GrDrawTarget(GrRenderTarget*, GrGpu*, GrResourceProvider*, const Options&);
 
     ~GrDrawTarget() override;
 
     void makeClosed() {
         // We only close drawTargets When MDB is enabled. When MDB is disabled there is only
         // ever one drawTarget and all calls will be funnelled into it.
 #ifdef ENABLE_MDB
@@ skipping 230 matching lines @@
     bool                                        fFlushing;
 
     SkDEBUGCODE(int                             fDebugID;)
     uint32_t                                    fFlags;
 
     // 'this' drawTarget relies on the output of the drawTargets in 'fDependencies'
     SkTDArray<GrDrawTarget*>                    fDependencies;
     GrRenderTarget*                             fRenderTarget;
 
     bool                                        fDrawBatchBounds;
+    int                                         fMaxBatchLookback;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif