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/ColorPrivBench.cpp b/bench/ColorPrivBench.cpp
index 4aa51c4..314f0cb 100644
--- a/bench/ColorPrivBench.cpp
+++ b/bench/ColorPrivBench.cpp
@@ -39,7 +39,7 @@
         if (kScale) fScales[256] = 255;  // We'll just do 255 twice if we're limited to [0,255].
     }
 
-    void onDraw(const int loops, SkCanvas*) override {
+    void onDraw(int loops, SkCanvas*) override {
         // We xor results of FourByteInterp into junk to make sure the function runs.
         volatile SkPMColor junk = 0;