move SkChecksum and SkEmptyShader to private

TBR=reed@google.com

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/366133002
diff --git a/tests/RecorderTest.cpp b/tests/RecorderTest.cpp
index c1d9638..5fcac4d 100644
--- a/tests/RecorderTest.cpp
+++ b/tests/RecorderTest.cpp
@@ -10,8 +10,7 @@
 #include "SkRecord.h"
 #include "SkRecorder.h"
 #include "SkRecords.h"
-
-#include "SkEmptyShader.h"
+#include "SkShader.h"
 
 #define COUNT(T) + 1
 static const int kRecordTypes = SK_RECORD_TYPES(COUNT);
@@ -57,7 +56,7 @@
 
     SkRect bounds = SkRect::MakeWH(320, 240);
     SkPaint paint;
-    paint.setShader(SkNEW(SkEmptyShader))->unref();
+    paint.setShader(SkShader::CreateEmptyShader())->unref();
 
     REPORTER_ASSERT(r, paint.getShader()->unique());
     {