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/DrawBitmapAABench.cpp b/bench/DrawBitmapAABench.cpp
index 9d5003b..011c30a 100644
--- a/bench/DrawBitmapAABench.cpp
+++ b/bench/DrawBitmapAABench.cpp
@@ -37,7 +37,7 @@
         fBitmap.eraseARGB(255, 0, 255, 0);
     }
 
-    void onDraw(const int loops, SkCanvas* canvas) override {
+    void onDraw(int loops, SkCanvas* canvas) override {
         canvas->concat(fMatrix);
         for (int i = 0; i < loops; i++) {
             canvas->drawBitmap(fBitmap, 0, 0, &fPaint);