When was SkPDiff last used?

tools/skpdiff/SkDifferentPixelsMetric.h

Index: tools/skpdiff/SkDifferentPixelsMetric.h
diff --git a/tools/skpdiff/SkDifferentPixelsMetric.h b/tools/skpdiff/SkDifferentPixelsMetric.h
deleted file mode 100644
index 1f39b3552e8e959544a417a534d6a5007ee1c699..0000000000000000000000000000000000000000
--- a/tools/skpdiff/SkDifferentPixelsMetric.h
+++ /dev/null
@@ -1,50 +0,0 @@
-/*
- * Copyright 2013 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkDifferentPixelsMetric_DEFINED
-#define SkDifferentPixelsMetric_DEFINED
-
-#include "SkTDArray.h"
-
-#if SK_SUPPORT_OPENCL
-#include "SkCLImageDiffer.h"
-#else
-#include "SkImageDiffer.h"
-#endif
-
-/**
- * A differ that measures the percentage of different corresponding pixels. If the two images are
- * not the same size or have no pixels, the result will always be zero.
- */
-class SkDifferentPixelsMetric :
-#if SK_SUPPORT_OPENCL
-    public SkCLImageDiffer {
-#else
-    public SkImageDiffer {
-#endif
-public:
-    const char* getName() const override;
-    virtual bool diff(SkBitmap* baseline, SkBitmap* test,
-                      const BitmapsToCreate& bitmapsToCreate,
-                      Result* result) const override;
-
-protected:
-#if SK_SUPPORT_OPENCL
-    bool onInit() override;
-#endif
-
-private:
-#if SK_SUPPORT_OPENCL
-    cl_kernel fKernel;
-
-    typedef SkCLImageDiffer INHERITED;
-#else
-    typedef SkImageDiffer INHERITED;
-#endif
-};
-
-#endif