Add MultiPictureDraw to nanobench

bench/Benchmark.cpp

Index: bench/Benchmark.cpp
diff --git a/bench/Benchmark.cpp b/bench/Benchmark.cpp
index 88e385d2d1840a841c9b0e6dc84c73107c4c7af7..6040f913ef3c7b3d107fe498ffd15a7df851aa72 100644
--- a/bench/Benchmark.cpp
+++ b/bench/Benchmark.cpp
@@ -37,6 +37,14 @@ void Benchmark::preDraw() {
     this->onPreDraw();
 }
 
+void Benchmark::perCanvasPreDraw(SkCanvas* canvas) {
+    this->onPerCanvasPreDraw(canvas);
+}
+
+void Benchmark::perCanvasPostDraw(SkCanvas* canvas) {
+    this->onPerCanvasPostDraw(canvas);
+}
+
 void Benchmark::draw(const int loops, SkCanvas* canvas) {
     SkAutoCanvasRestore ar(canvas, true/*save now*/);
     this->onDraw(loops, canvas);