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.cpp b/bench/SKPBench.cpp
index f0dafb6..4426133 100644
--- a/bench/SKPBench.cpp
+++ b/bench/SKPBench.cpp
@@ -104,7 +104,7 @@
     return SkIPoint::Make(fClip.width(), fClip.height());
 }
 
-void SKPBench::onDraw(const int loops, SkCanvas* canvas) {
+void SKPBench::onDraw(int loops, SkCanvas* canvas) {
     SkASSERT(fDoLooping || 1 == loops);
     if (fUseMultiPictureDraw) {
         for (int i = 0; i < loops; i++) {