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/ChartBench.cpp b/bench/ChartBench.cpp
index 8b3aa73..c5a3a5b 100644
--- a/bench/ChartBench.cpp
+++ b/bench/ChartBench.cpp
@@ -104,7 +104,7 @@
         }
     }
 
-    void onDraw(const int loops, SkCanvas* canvas) override {
+    void onDraw(int loops, SkCanvas* canvas) override {
         bool sizeChanged = false;
         if (canvas->getDeviceSize() != fSize) {
             fSize = canvas->getDeviceSize();