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/CoverageBench.cpp b/bench/CoverageBench.cpp
index 135ef39..3dee668 100644
--- a/bench/CoverageBench.cpp
+++ b/bench/CoverageBench.cpp
@@ -48,7 +48,7 @@
         return fName.c_str();
     }
 
-    void onDraw(const int loops, SkCanvas* canvas) override {
+    void onDraw(int loops, SkCanvas* canvas) override {
         if (fDrawCoverage) {
             for (int i = 0; i < loops; ++i) {
                 fDraw.drawPathCoverage(fPath, fPaint);