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/RectanizerBench.cpp b/bench/RectanizerBench.cpp
index 99f10c0..286b681 100644
--- a/bench/RectanizerBench.cpp
+++ b/bench/RectanizerBench.cpp
@@ -5,7 +5,7 @@
 * found in the LICENSE file.
 */
 
-#include "SkBenchmark.h"
+#include "Benchmark.h"
 #include "SkRandom.h"
 #include "SkSize.h"
 #include "SkTDArray.h"
@@ -25,7 +25,7 @@
  *      random power of two rects
  *      small constant sized power of 2 rects (e.g., glyph cache use case)
  */
-class RectanizerBench : public SkBenchmark {
+class RectanizerBench : public Benchmark {
 public:
     static const int kWidth = 1024;
     static const int kHeight = 1024;
@@ -117,7 +117,7 @@
     RectType                    fRectType;
     SkAutoTDelete<GrRectanizer> fRectanizer;
 
-    typedef SkBenchmark INHERITED;
+    typedef Benchmark INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////