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/WriterBench.cpp b/bench/WriterBench.cpp
index 6db1cf1..115ffc1 100644
--- a/bench/WriterBench.cpp
+++ b/bench/WriterBench.cpp
@@ -21,7 +21,7 @@
         return "writer";
     }
 
-    void onDraw(const int loops, SkCanvas*) override {
+    void onDraw(int loops, SkCanvas*) override {
         static const char gStr[] = "abcdefghimjklmnopqrstuvwxyz";
         static const size_t gLen = strlen(gStr);
         SkWriter32 writer;