Revert of Hide SkCanvas::LayerIter

tools/VisualBench/WrappedBenchmark.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef WrappedBenchmark_DEFINED
 #define WrappedBenchmark_DEFINED
 
 #include "Benchmark.h"
+#include "SkDevice.h"
 #include "SkSurface.h"
 #include "GrContext.h"
 #include "GrRenderTarget.h"
 
 // Wrap some other benchmark to allow specialization to either
 // cpu or gpu backends. The derived class will override 'setupOffScreen'
 // to create an offscreen surface in which the actual rendering will occur.
 class WrappedBenchmark : public Benchmark {
 public:
     // Takes ownership of caller's ref on `bench`.
@@ skipping 83 matching lines @@
     void setupOffScreen(SkCanvas* canvas) override {
         fOffScreen = SkSurface::MakeRenderTarget(canvas->getGrContext(),
                                                     SkBudgeted::kNo,
                                                     canvas->imageInfo(),
                                                     fNumSamples,
                                                     &this->surfaceProps());
     }
 
     void onBlitToScreen(SkCanvas* canvas, int w, int h) override {
         // We call copySurface directly on the underlying GPU surfaces for a more efficient blit.
-        GrRenderTarget* dst = canvas->internal_private_accessTopLayerRenderTarget();
-        SkASSERT(dst);
+        GrRenderTarget* dst, *src;
 
-        GrRenderTarget* src = fOffScreen->getCanvas()->internal_private_accessTopLayerRenderTarget();
-        SkASSERT(src);
+        SkCanvas::LayerIter canvasIter(canvas, false);
+        SkAssertResult((dst = canvasIter.device()->accessRenderTarget()));
+
+        SkCanvas::LayerIter offscreenIter(fOffScreen->getCanvas(), false);
+        SkAssertResult((src = offscreenIter.device()->accessRenderTarget()));
 
         SkASSERT(dst->getContext() == src->getContext());
 
         dst->getContext()->copySurface(dst, src, SkIRect::MakeWH(w, h), SkIPoint::Make(0, 0));
+
+#ifdef SK_DEBUG
+        // This method should not be called while layers are saved.
+        canvasIter.next();
+        SkASSERT(canvasIter.done());
+
+        offscreenIter.next();
+        SkASSERT(offscreenIter.done());
+#endif
     }
 
     int fNumSamples;
     typedef WrappedBenchmark INHERITED;
 };
 
 #endif //WrappedBenchmark_DEFINED