Plumb through out_row byte length so we can assert we stay underneath it.

src/opts/SkBitmapFilter_opts_SSE2.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBitmapFilter_opts_sse2_DEFINED
 #define SkBitmapFilter_opts_sse2_DEFINED
 
 #include "SkBitmapProcState.h"
 #include "SkConvolver.h"
 
 void convolveVertically_SSE2(const SkConvolutionFilter1D::ConvolutionFixed* filter_values,
                              int filter_length,
                              unsigned char* const* source_data_rows,
                              int pixel_width,
                              unsigned char* out_row,
                              bool has_alpha);
 void convolve4RowsHorizontally_SSE2(const unsigned char* src_data[4],
                                     const SkConvolutionFilter1D& filter,
-                                    unsigned char* out_row[4]);
+                                    unsigned char* out_row[4],
+                                    size_t outRowBytes);
 void convolveHorizontally_SSE2(const unsigned char* src_data,
                                const SkConvolutionFilter1D& filter,
                                unsigned char* out_row,
                                bool has_alpha);
 void applySIMDPadding_SSE2(SkConvolutionFilter1D* filter);
 
 #endif