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/BitmapRegionDecoderBench.h b/bench/BitmapRegionDecoderBench.h
index 4f4d55e..3f3da6c 100644
--- a/bench/BitmapRegionDecoderBench.h
+++ b/bench/BitmapRegionDecoderBench.h
@@ -33,7 +33,7 @@
 protected:
     const char* onGetName() override;
     bool isSuitableFor(Backend backend) override;
-    void onDraw(const int n, SkCanvas* canvas) override;
+    void onDraw(int n, SkCanvas* canvas) override;
     void onDelayedSetup() override;
 
 private: