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/FontCacheBench.cpp b/bench/FontCacheBench.cpp
index a3c0672..0e75c9c 100644
--- a/bench/FontCacheBench.cpp
+++ b/bench/FontCacheBench.cpp
@@ -5,7 +5,7 @@
  * found in the LICENSE file.
  */
 
-#include "SkBenchmark.h"
+#include "Benchmark.h"
 #include "SkCanvas.h"
 #include "SkFontHost.h"
 #include "SkPaint.h"
@@ -23,7 +23,7 @@
     return static_cast<int>(curr - start);
 }
 
-class FontCacheBench : public SkBenchmark {
+class FontCacheBench : public Benchmark {
 public:
     FontCacheBench()  {}
 
@@ -48,7 +48,7 @@
     }
 
 private:
-    typedef SkBenchmark INHERITED;
+    typedef Benchmark INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -107,7 +107,7 @@
     SkDebugf("\n");
 }
 
-class FontCacheEfficiency : public SkBenchmark {
+class FontCacheEfficiency : public Benchmark {
 public:
     FontCacheEfficiency()  {
         if (false) dump_array(NULL, 0);
@@ -147,7 +147,7 @@
     }
 
 private:
-    typedef SkBenchmark INHERITED;
+    typedef Benchmark INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////