Add MultiPictureDraw to nanobench

bench/Benchmark.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef Benchmark_DEFINED
 #define Benchmark_DEFINED
 
@@ skipping 52 matching lines @@
     // the rendering mode.
     virtual bool isSuitableFor(Backend backend) {
         return backend != kNonRendering_Backend;
     }
 
     // Call before draw, allows the benchmark to do setup work outside of the
     // timer. When a benchmark is repeatedly drawn, this should be called once
     // before the initial draw.
     void preDraw();
 
+    // Called once before and after a series of draw calls to a single canvas.
+    // The setup/break down in these calls is not timed.
+    void perCanvasPreDraw(SkCanvas*);
+    void perCanvasPostDraw(SkCanvas*);
+
     // Bench framework can tune loops to be large enough for stable timing.
     void draw(const int loops, SkCanvas*);
 
     void setForceAlpha(int alpha) {
         fForceAlpha = alpha;
     }
 
     void setDither(SkTriState::State state) {
         fDither = state;
     }
@@ skipping 11 matching lines @@
         fOrMask = orMask;
         fClearMask = clearMask;
     }
 
 protected:
     virtual void setupPaint(SkPaint* paint);
 
     virtual const char* onGetName() = 0;
     virtual const char* onGetUniqueName() { return this->onGetName(); }
     virtual void onPreDraw() {}
+    virtual void onPerCanvasPreDraw(SkCanvas*) {}
+    virtual void onPerCanvasPostDraw(SkCanvas*) {}
     // Each bench should do its main work in a loop like this:
     //   for (int i = 0; i < loops; i++) { <work here> }
     virtual void onDraw(const int loops, SkCanvas*) = 0;
 
     virtual SkIPoint onGetSize();
 
 private:
     int     fForceAlpha;
     SkTriState::State  fDither;
     uint32_t    fOrMask, fClearMask;
 
     typedef SkRefCnt INHERITED;
 };
 
 typedef SkTRegistry<Benchmark*(*)(void*)> BenchRegistry;
 
 #endif