Remove Sk prefix from some bench classes.

bench/MutexBench.cpp

Index: bench/MutexBench.cpp
diff --git a/bench/MutexBench.cpp b/bench/MutexBench.cpp
index 3191ce17bef53c81f25ed50b812d26e1716c6b66..67648b5decf31bbf257eba39f495c00e1d4dbf2d 100644
--- a/bench/MutexBench.cpp
+++ b/bench/MutexBench.cpp
@@ -4,10 +4,10 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
-#include "SkBenchmark.h"
+#include "Benchmark.h"
 #include "SkThread.h"
 
-class MutexBench : public SkBenchmark {
+class MutexBench : public Benchmark {
 public:
     virtual bool isSuitableFor(Backend backend) SK_OVERRIDE {
         return backend == kNonRendering_Backend;
@@ -27,7 +27,7 @@ protected:
     }
 
 private:
-    typedef SkBenchmark INHERITED;
+    typedef Benchmark INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////