just add SkLiteDL::empty()

src/core/SkLiteDL.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkLiteDL_DEFINED
 #define SkLiteDL_DEFINED
 
 #include "SkCanvas.h"
 #include "SkPaint.h"
 #include "SkPath.h"
 #include "SkDrawable.h"
 #include "SkRect.h"
 #include "SkTDArray.h"
 
 class GrContext;
 
 class SkLiteDL final : public SkDrawable {
 public:
     static sk_sp<SkLiteDL> New(SkRect);
 
     static void PurgeFreelist();
 
     void optimizeFor(GrContext*);
     void makeThreadsafe();
+    bool empty() const;
 
     void save();
     void saveLayer(const SkRect*, const SkPaint*, const SkImageFilter*, SkCanvas::SaveLayerFlags);
     void restore();
 
     void    concat (const SkMatrix&);
     void setMatrix (const SkMatrix&);
     void translateZ(SkScalar);
 
     void clipPath  (const   SkPath&, SkRegion::Op, bool aa);
@@ skipping 58 matching lines @@
     size_t                 fUsed;
     size_t                 fReserved;
     SkRect                 fBounds;
 
     // Only used for freelisting.
     SkLiteDL* fNext;
     int       fUsesRemaining;
 };
 
 #endif//SkLiteDL_DEFINED