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/PictureOverheadBench.cpp b/bench/PictureOverheadBench.cpp
index c9dedf4..62a51ec 100644
--- a/bench/PictureOverheadBench.cpp
+++ b/bench/PictureOverheadBench.cpp
@@ -19,7 +19,7 @@
     }
     bool isSuitableFor(Backend backend) override { return backend == kNonRendering_Backend; }
 
-    void onDraw(const int loops, SkCanvas*) override {
+    void onDraw(int loops, SkCanvas*) override {
         SkPictureRecorder rec;
         for (int i = 0; i < loops; i++) {
             rec.beginRecording(SkRect::MakeWH(2000,3000));