Simplify benchmark internal API.

bench/MutexBench.cpp

Index: bench/MutexBench.cpp
diff --git a/bench/MutexBench.cpp b/bench/MutexBench.cpp
index bec0c8058c92b0f39ff3d094039531847c205ea1..3191ce17bef53c81f25ed50b812d26e1716c6b66 100644
--- a/bench/MutexBench.cpp
+++ b/bench/MutexBench.cpp
@@ -18,9 +18,9 @@ protected:
         return "mutex";
     }
 
-    virtual void onDraw(SkCanvas*) {
+    virtual void onDraw(const int loops, SkCanvas*) {
         SK_DECLARE_STATIC_MUTEX(mu);
-        for (int i = 0; i < this->getLoops(); i++) {
+        for (int i = 0; i < loops; i++) {
             mu.acquire();
             mu.release();
         }