Revert of Hide SkCanvas::LayerIter

tools/VisualBench/WrappedBenchmark.h

Index: tools/VisualBench/WrappedBenchmark.h
diff --git a/tools/VisualBench/WrappedBenchmark.h b/tools/VisualBench/WrappedBenchmark.h
index ddf601ddf8331ed80a1b32eccaeafa2d7f43dd05..bd88f13502ead965cb79cc2a0c182c639a59fd22 100644
--- a/tools/VisualBench/WrappedBenchmark.h
+++ b/tools/VisualBench/WrappedBenchmark.h
@@ -9,6 +9,7 @@
 #define WrappedBenchmark_DEFINED
 
 #include "Benchmark.h"
+#include "SkDevice.h"
 #include "SkSurface.h"
 #include "GrContext.h"
 #include "GrRenderTarget.h"
@@ -112,15 +113,26 @@
 
     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;