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/WritePixelsBench.cpp b/bench/WritePixelsBench.cpp
index 0b98cf8..d9f8eb7 100644
--- a/bench/WritePixelsBench.cpp
+++ b/bench/WritePixelsBench.cpp
@@ -45,7 +45,7 @@
         return fName.c_str();
     }
 
-    void onDraw(const int loops, SkCanvas* canvas) override {
+    void onDraw(int loops, SkCanvas* canvas) override {
         SkISize size = canvas->getDeviceSize();
 
         canvas->clear(0xFFFF0000);