diff -r 000000000000 -r 6474c204b198 gfx/skia/trunk/src/utils/SkBitmapHasher.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/skia/trunk/src/utils/SkBitmapHasher.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,35 @@
+
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkBitmapHasher_DEFINED
+#define SkBitmapHasher_DEFINED
+
+#include "SkBitmap.h"
+
+/**
+ * Static class that generates a uint64 hash digest from an SkBitmap.
+ */
+class SkBitmapHasher {
+public:
+    /**
+     * Fills in "result" with a hash of the pixels in this bitmap.
+     *
+     * If this is unable to compute the hash for some reason,
+     * it returns false.
+     *
+     * Note: depending on the bitmap config, we may need to create an
+     * intermediate SkBitmap and copy the pixels over to it... so in some
+     * cases, performance and memory usage can suffer.
+     */
+    static bool ComputeDigest(const SkBitmap& bitmap, uint64_t *result);
+
+private:
+    static bool ComputeDigestInternal(const SkBitmap& bitmap, uint64_t *result);
+};
+
+#endif