SSE2 implementation of RGBA box blurs. This yields ~2X perf improvement on

src/opts/SkBlurImage_opts.h

+/*
+ * Copyright 2013 The Android Open Source Project
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkBlurImage_opts_DEFINED
+#define SkBlurImage_opts_DEFINED
+
+#include "SkColorPriv.h"
+
+typedef void (*SkBoxBlurProc)(const SkPMColor* src, int srcStride, SkPMColor* dst, int kernelSize,
+                              int leftOffset, int rightOffset, int width, int height);
+
+enum SkBlurDirection {
+    kX_BlurDirection, kY_BlurDirection
+};
+
+SkBoxBlurProc SkBoxBlurGetPlatformProc(SkBlurDirection srcDirection, SkBlurDirection dstDirection);
+#endif