stop scaling loops and improve warmup bench

bench/RectBench.cpp

Index: bench/RectBench.cpp
diff --git a/bench/RectBench.cpp b/bench/RectBench.cpp
index f793c8ff57124758c567ed33f3189dfccfe7c32d..23fb7c50c26c5af12435ca4f28e216f1c739e231 100644
--- a/bench/RectBench.cpp
+++ b/bench/RectBench.cpp
@@ -114,6 +114,30 @@ private:
     typedef RectBench INHERITED;
 };
 
+class TransparentRectBench : public RectBench {
+public:
+    TransparentRectBench() : INHERITED(1, 0) {}
+
+protected:
+    void setupPaint(SkPaint* paint) override {
+        this->INHERITED::setupPaint(paint);
+        // draw non opaque rect
+        paint->setAlpha(0x80);
+    }
+
+    const char* onGetName() override {
+        fName.set(this->INHERITED::onGetName());
+        fName.prepend("transparent_");
+        return fName.c_str();
+    }
+
+private:
+    SkString fName;
+
+    typedef RectBench INHERITED;
+};
+
+
 class OvalBench : public RectBench {
 public:
     OvalBench(int shift, int stroke = 0) : RectBench(shift, stroke) {}
@@ -269,6 +293,8 @@ DEF_BENCH(return new PointsBench(SkCanvas::kPolygon_PointMode, "polygon");)
 
 DEF_BENCH(return new SrcModeRectBench();)
 
+DEF_BENCH(return new TransparentRectBench();)
+
 /* init the blitmask bench
  */
 DEF_BENCH(return new BlitMaskBench(SkCanvas::kPoints_PointMode,