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/dm/DM.cpp b/dm/DM.cpp
index fde057d..2981013 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -1,7 +1,8 @@
 // Main binary for DM.
 // For a high-level overview, please see dm/README.
 
-#include "SkBenchmark.h"
+#include "Benchmark.h"
+#include "CrashHandler.h"
 #include "SkCommandLineFlags.h"
 #include "SkForceLinking.h"
 #include "SkGraphics.h"
@@ -9,7 +10,6 @@
 #include "SkString.h"
 #include "Test.h"
 #include "gm.h"
-#include "CrashHandler.h"
 
 #include "DMBenchTask.h"
 #include "DMCpuGMTask.h"
@@ -249,7 +249,7 @@
 
     SkTDArray<BenchRegistry::Factory> benches;
     if (FLAGS_benches) {
-        append_matching_factories<SkBenchmark>(BenchRegistry::Head(), &benches);
+        append_matching_factories<Benchmark>(BenchRegistry::Head(), &benches);
     }
 
     SkTDArray<TestRegistry::Factory> tests;