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/GLBench.cpp b/bench/GLBench.cpp
index 23dd04f..e51adba 100644
--- a/bench/GLBench.cpp
+++ b/bench/GLBench.cpp
@@ -50,7 +50,7 @@
     this->teardown(ctx->interface());
 }
 
-void GLBench::onDraw(const int loops, SkCanvas* canvas) {
+void GLBench::onDraw(int loops, SkCanvas* canvas) {
     const GrGLContext* ctx = this->getGLContext(canvas);
     if (!ctx) {
         return;