Remove Sk prefix from some bench classes.

This idea came while commenting on
https://codereview.chromium.org/343583005/

Since SkBenchmark, SkBenchLogger and SkGMBench are not part of the Skia library,
they should not have the Sk prefix.

BUG=None
TEST=make all
R=mtklein@google.com

Author: tfarina@chromium.org

Review URL: https://codereview.chromium.org/347823004
diff --git a/bench/MatrixConvolutionBench.cpp b/bench/MatrixConvolutionBench.cpp
index 77910c9..6593ab0 100644
--- a/bench/MatrixConvolutionBench.cpp
+++ b/bench/MatrixConvolutionBench.cpp
@@ -4,14 +4,14 @@
  * 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 "SkCanvas.h"
+#include "SkMatrixConvolutionImageFilter.h"
 #include "SkPaint.h"
 #include "SkRandom.h"
 #include "SkString.h"
-#include "SkMatrixConvolutionImageFilter.h"
 
-class MatrixConvolutionBench : public SkBenchmark {
+class MatrixConvolutionBench : public Benchmark {
 public:
     MatrixConvolutionBench(SkMatrixConvolutionImageFilter::TileMode tileMode, bool convolveAlpha)
         : fName("matrixconvolution") {
@@ -49,7 +49,7 @@
     }
 
 private:
-    typedef SkBenchmark INHERITED;
+    typedef Benchmark INHERITED;
     SkMatrixConvolutionImageFilter* fFilter;
     SkString fName;
 };