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/nanobench.cpp b/bench/nanobench.cpp
index 6328aa1..a7a47c5 100644
--- a/bench/nanobench.cpp
+++ b/bench/nanobench.cpp
@@ -1182,7 +1182,7 @@
             bench->perCanvasPreDraw(canvas);
 
             int maxFrameLag;
-            const int loops = target->needsFrameTiming(&maxFrameLag)
+            int loops = target->needsFrameTiming(&maxFrameLag)
                 ? setup_gpu_bench(target, bench.get(), maxFrameLag)
                 : setup_cpu_bench(overhead, target, bench.get());