diff -r 000000000000 -r 6474c204b198 gfx/skia/trunk/src/core/SkBitmap_scroll.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/skia/trunk/src/core/SkBitmap_scroll.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,105 @@
+
+/*
+ * Copyright 2011 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "SkBitmap.h"
+#include "SkRegion.h"
+
+bool SkBitmap::scrollRect(const SkIRect* subset, int dx, int dy,
+                          SkRegion* inval) const
+{
+    if (this->isImmutable() || kUnknown_SkColorType == this->colorType()) {
+        return false;
+    }
+
+    if (NULL != subset) {
+        SkBitmap tmp;
+
+        return  this->extractSubset(&tmp, *subset) &&
+                // now call again with no rectangle
+                tmp.scrollRect(NULL, dx, dy, inval);
+    }
+
+    int shift = this->bytesPerPixel() >> 1;
+    int width = this->width();
+    int height = this->height();
+
+    // check if there's nothing to do
+    if ((dx | dy) == 0 || width <= 0 || height <= 0) {
+        if (NULL != inval) {
+            inval->setEmpty();
+        }
+        return true;
+    }
+
+    // compute the inval region now, before we see if there are any pixels
+    if (NULL != inval) {
+        SkIRect r;
+
+        r.set(0, 0, width, height);
+        // initial the region with the entire bounds
+        inval->setRect(r);
+        // do the "scroll"
+        r.offset(dx, dy);
+
+        // check if we scrolled completely away
+        if (!SkIRect::Intersects(r, inval->getBounds())) {
+            // inval has already been updated...
+            return true;
+        }
+
+        // compute the dirty area
+        inval->op(r, SkRegion::kDifference_Op);
+    }
+
+    SkAutoLockPixels    alp(*this);
+    // if we have no pixels, just return (inval is already updated)
+    // don't call readyToDraw(), since we don't require a colortable per se
+    if (this->getPixels() == NULL) {
+        return true;
+    }
+
+    char*       dst = (char*)this->getPixels();
+    const char* src = dst;
+    int         rowBytes = (int)this->rowBytes();    // need rowBytes to be signed
+
+    if (dy <= 0) {
+        src -= dy * rowBytes;
+        height += dy;
+    } else {
+        dst += dy * rowBytes;
+        height -= dy;
+        // now jump src/dst to the last scanline
+        src += (height - 1) * rowBytes;
+        dst += (height - 1) * rowBytes;
+        // now invert rowbytes so we copy backwards in the loop
+        rowBytes = -rowBytes;
+    }
+
+    if (dx <= 0) {
+        src -= dx << shift;
+        width += dx;
+    } else {
+        dst += dx << shift;
+        width -= dx;
+    }
+
+    // If the X-translation would push it completely beyond the region,
+    // then there's nothing to draw.
+    if (width <= 0) {
+        return true;
+    }
+
+    width <<= shift;    // now width is the number of bytes to move per line
+    while (--height >= 0) {
+        memmove(dst, src, width);
+        dst += rowBytes;
+        src += rowBytes;
+    }
+
+    this->notifyPixelsChanged();
+    return true;
+}