Remove const from `const int loops`.

This drives me nuts, and prevents `while (loops --> 0)`.

BUG=skia:

Review URL: https://codereview.chromium.org/1379923005
diff --git a/bench/SKPBench.h b/bench/SKPBench.h
index 05b5857..89c9a36 100644
--- a/bench/SKPBench.h
+++ b/bench/SKPBench.h
@@ -34,7 +34,7 @@
     void onPerCanvasPreDraw(SkCanvas*) override;
     void onPerCanvasPostDraw(SkCanvas*) override;
     bool isSuitableFor(Backend backend) override;
-    void onDraw(const int loops, SkCanvas* canvas) override;
+    void onDraw(int loops, SkCanvas* canvas) override;
     SkIPoint onGetSize() override;
 
     virtual void drawMPDPicture();