When was SkPDiff last used?

tools/skpdiff/SkImageDiffer.cpp

Index: tools/skpdiff/SkImageDiffer.cpp
diff --git a/tools/skpdiff/SkImageDiffer.cpp b/tools/skpdiff/SkImageDiffer.cpp
deleted file mode 100644
index 2ceba6d80e6ac0036ff79773f0ad23779b42a1fc..0000000000000000000000000000000000000000
--- a/tools/skpdiff/SkImageDiffer.cpp
+++ /dev/null
@@ -1,19 +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.
- */
-
-#include "SkImageDiffer.h"
-
-const double SkImageDiffer::RESULT_CORRECT = 1.0f;
-const double SkImageDiffer::RESULT_INCORRECT = 0.0f;
-
-SkImageDiffer::SkImageDiffer() {
-
-}
-
-SkImageDiffer::~SkImageDiffer() {
-
-}