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/XfermodeBench.cpp b/bench/XfermodeBench.cpp
index 7e61826..f407c59 100644
--- a/bench/XfermodeBench.cpp
+++ b/bench/XfermodeBench.cpp
@@ -33,7 +33,7 @@
 protected:
     const char* onGetName() override { return fName.c_str(); }
 
-    void onDraw(const int loops, SkCanvas* canvas) override {
+    void onDraw(int loops, SkCanvas* canvas) override {
         const char* text = "Hamburgefons";
         size_t len = strlen(text);
         SkISize size = canvas->getDeviceSize();
@@ -85,7 +85,7 @@
 protected:
     const char* onGetName() override { return "xfermode_create"; }
 
-    void onDraw(const int loops, SkCanvas* canvas) override {
+    void onDraw(int loops, SkCanvas* canvas) override {
         for (int outer = 0; outer < loops * 10; ++outer) {
             for (int i = 0; i <= SkXfermode::kLastMode; ++i) {
                 SkXfermode* xfer = SkXfermode::Create(SkXfermode::Mode(i));