When was SkPDiff last used?

tools/skpdiff/SkImageDiffer.h

Index: tools/skpdiff/SkImageDiffer.h
diff --git a/tools/skpdiff/SkImageDiffer.h b/tools/skpdiff/SkImageDiffer.h
deleted file mode 100644
index 7960057bc4167beb8627aaa587516b01d5f0717c..0000000000000000000000000000000000000000
--- a/tools/skpdiff/SkImageDiffer.h
+++ /dev/null
@@ -1,73 +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 SkImageDiffer_DEFINED
-#define SkImageDiffer_DEFINED
-
-#include "SkBitmap.h"
-
-/**
- * Encapsulates an image difference metric algorithm that can be potentially run asynchronously.
- */
-class SkImageDiffer {
-public:
-    SkImageDiffer();
-    virtual ~SkImageDiffer();
-
-    static const double RESULT_CORRECT;
-    static const double RESULT_INCORRECT;
-
-    struct Result {
-        double result;
-        int poiCount;
-        // TODO(djsollen): Figure out a way that the differ can report which of the
-        // optional fields it has filled in.  See https://bug.skia.org/2712 ('allow
-        // skpdiff to report different sets of result fields for different comparison algorithms')
-        SkBitmap poiAlphaMask; // optional
-        SkBitmap rgbDiffBitmap; // optional
-        SkBitmap whiteDiffBitmap; // optional
-        int maxRedDiff; // optional
-        int maxGreenDiff; // optional
-        int maxBlueDiff; // optional
-        double timeElapsed; // optional
-    };
-
-    // A bitfield indicating which bitmap types we want a differ to create.
-    //
-    // TODO(epoger): Remove whiteDiffBitmap, because alphaMask can provide
-    // the same functionality and more.
-    // It will be a little bit tricky, because the rebaseline_server client
-    // and server side code will both need to change to use the alphaMask.
-    struct BitmapsToCreate {
-        bool alphaMask;
-        bool rgbDiff;
-        bool whiteDiff;
-    };
-
-    /**
-     * Gets a unique and descriptive name of this differ
-     * @return A statically allocated null terminated string that is the name of this differ
-     */
-    virtual const char* getName() const = 0;
-
-    /**
-     * Gets if this differ needs to be initialized with and OpenCL device and context.
-     */
-    virtual bool requiresOpenCL() const { return false; }
-
-    /**
-     * diff on a pair of bitmaps.
-     * @param  baseline    The correct bitmap
-     * @param  test        The bitmap whose difference is being tested
-     * @param  bitmapsToCreate  Which bitmaps the differ should attempt to create
-     * @return             true on success, and false in the case of failure
-     */
-    virtual bool diff(SkBitmap* baseline, SkBitmap* test, const BitmapsToCreate& bitmapsToCreate,
-                      Result* result) const = 0;
-};
-
-#endif