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/PathIterBench.cpp b/bench/PathIterBench.cpp
index 4e956ce..b82146d 100644
--- a/bench/PathIterBench.cpp
+++ b/bench/PathIterBench.cpp
@@ -5,7 +5,7 @@
  * 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 "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkColorPriv.h"
@@ -25,7 +25,7 @@
     return n;
 }
 
-class PathIterBench : public SkBenchmark {
+class PathIterBench : public Benchmark {
     SkString    fName;
     SkPath      fPath;
     bool        fRaw;
@@ -86,7 +86,7 @@
     }
 
 private:
-    typedef SkBenchmark INHERITED;
+    typedef Benchmark INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////