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/ImageBench.cpp b/bench/ImageBench.cpp
index 69ab17f..89fbcd6 100644
--- a/bench/ImageBench.cpp
+++ b/bench/ImageBench.cpp
@@ -39,7 +39,7 @@
         fRasterSurface.reset(SkSurface::NewRaster(info));
     }
 
-    void onDraw(const int loops, SkCanvas*) override {
+    void onDraw(int loops, SkCanvas*) override {
         for (int i = 0; i < loops; i++) {
             for (int inner = 0; inner < 10; ++inner) {
                 fRasterSurface->getCanvas()->drawImage(fImage, 0, 0);