diff -r 000000000000 -r 6474c204b198 gfx/layers/BufferUnrotate.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/layers/BufferUnrotate.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,64 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <algorithm> // min & max
+#include <cstdlib>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void BufferUnrotate(uint8_t* aBuffer, int aByteWidth, int aHeight,
+                    int aByteStride, int aXBoundary, int aYBoundary)
+{
+  if (aXBoundary != 0) {
+    uint8_t* line = new uint8_t[aByteWidth];
+    uint32_t smallStart = 0;
+    uint32_t smallLen = aXBoundary;
+    uint32_t smallDest = aByteWidth - aXBoundary;
+    uint32_t largeStart = aXBoundary;
+    uint32_t largeLen = aByteWidth - aXBoundary;
+    uint32_t largeDest = 0;
+    if (aXBoundary > aByteWidth / 2) {
+      smallStart = aXBoundary;
+      smallLen = aByteWidth - aXBoundary;
+      smallDest = 0;
+      largeStart = 0;
+      largeLen = aXBoundary;
+      largeDest = smallLen;
+    }
+
+    for (int y = 0; y < aHeight; y++) {
+      int yOffset = y * aByteStride;
+      memcpy(line, &aBuffer[yOffset + smallStart], smallLen);
+      memmove(&aBuffer[yOffset + largeDest], &aBuffer[yOffset + largeStart], largeLen);
+      memcpy(&aBuffer[yOffset + smallDest], line, smallLen);
+    }
+
+    delete[] line;
+  }
+
+  if (aYBoundary != 0) {
+    uint32_t smallestHeight = std::min(aHeight - aYBoundary, aYBoundary);
+    uint32_t largestHeight = std::max(aHeight - aYBoundary, aYBoundary);
+    uint32_t smallOffset = 0;
+    uint32_t largeOffset = aYBoundary * aByteStride;
+    uint32_t largeDestOffset = 0;
+    uint32_t smallDestOffset = largestHeight * aByteStride;
+    if (aYBoundary > aHeight / 2) {
+      smallOffset = aYBoundary * aByteStride;
+      largeOffset = 0;
+      largeDestOffset = smallestHeight * aByteStride;
+      smallDestOffset = 0;
+    }
+
+    uint8_t* smallestSide = new uint8_t[aByteStride * smallestHeight];
+    memcpy(smallestSide, &aBuffer[smallOffset], aByteStride * smallestHeight);
+    memmove(&aBuffer[largeDestOffset], &aBuffer[largeOffset], aByteStride * largestHeight);
+    memcpy(&aBuffer[smallDestOffset], smallestSide, aByteStride * smallestHeight);
+    delete[] smallestSide;
+  }
+}
+