Revert of Add gpu implementation of OverdrawXfermode

src/utils/debugger/SkOverdrawMode.h

Index: src/utils/debugger/SkOverdrawMode.h
diff --git a/src/utils/debugger/SkOverdrawMode.h b/src/utils/debugger/SkOverdrawMode.h
deleted file mode 100644
index dba7635f6a32a05a652553d3f6d1ebdae1d974da..0000000000000000000000000000000000000000
--- a/src/utils/debugger/SkOverdrawMode.h
+++ /dev/null
@@ -1,25 +0,0 @@
-/*
- * Copyright 2016 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkOverdrawMode_DEFINED
-#define SkOverdrawMode_DEFINED
-
-#include "SkFlattenable.h"
-
-class SkXfermode;
-
-class SkOverdrawMode {
-public:
-    static SkXfermode* Create();
-
-    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP();
-
-private:
-    SkOverdrawMode(); // can't be instantiated
-};
-
-#endif