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/BlurRectBench.cpp b/bench/BlurRectBench.cpp
index 6871e0e..cdcdfe5 100644
--- a/bench/BlurRectBench.cpp
+++ b/bench/BlurRectBench.cpp
@@ -5,13 +5,13 @@
  * found in the LICENSE file.
  */
 
-#include "SkBenchmark.h"
+#include "Benchmark.h"
+#include "SkBlurMask.h"
 #include "SkCanvas.h"
 #include "SkPaint.h"
 #include "SkRandom.h"
 #include "SkShader.h"
 #include "SkString.h"
-#include "SkBlurMask.h"
 
 #define SMALL   SkIntToScalar(2)
 #define REAL    1.5f
@@ -20,7 +20,7 @@
 static const SkScalar kMedBig = SkIntToScalar(20);
 #define REALBIG 30.5f
 
-class BlurRectBench: public SkBenchmark {
+class BlurRectBench: public Benchmark {
     int         fLoopCount;
     SkScalar    fRadius;
     SkString    fName;
@@ -70,7 +70,7 @@
     virtual void makeBlurryRect(const SkRect&) = 0;
     virtual void preBenchSetup(const SkRect&) {}
 private:
-    typedef SkBenchmark INHERITED;
+    typedef Benchmark INHERITED;
 };