Change prototypes to yuv_convert_simd_x86 yasm and equivalent C to portably sign extend int args

media/base/simd/convert_rgb_to_yuv_ssse3.h

Index: media/base/simd/convert_rgb_to_yuv_ssse3.h
diff --git a/media/base/simd/convert_rgb_to_yuv_ssse3.h b/media/base/simd/convert_rgb_to_yuv_ssse3.h
index 84557d197facb77ca4e6c4b780f9ae3d4edb4593..92144c9aaca15e6742e8406c3d9e1feeb9e450ae 100644
--- a/media/base/simd/convert_rgb_to_yuv_ssse3.h
+++ b/media/base/simd/convert_rgb_to_yuv_ssse3.h
@@ -13,19 +13,25 @@ extern "C" {
 // instructions so we can call them from C++ code. These functions are
 // implemented in "convert_rgb_to_yuv_ssse3.asm".
 
+// We use ptrdiff_t instead of int for yasm routine parameters to portably
+// sign-extend int. On Win64, MSVC does not sign-extend the value in the stack
+// home of int function parameters, and yasm routines are unaware of this lack
+// of extension and fault.  ptrdiff_t is portably sign-extended and fixes this
+// issue on at least Win64.
+
 // Convert a row of 24-bit RGB pixels to YV12 pixels.
 void ConvertRGBToYUVRow_SSSE3(const uint8* rgb,
                               uint8* y,
                               uint8* u,
                               uint8* v,
-                              int width);
+                              ptrdiff_t width);
 
 // Convert a row of 32-bit RGB pixels to YV12 pixels.
 void ConvertARGBToYUVRow_SSSE3(const uint8* argb,
                                uint8* y,
                                uint8* u,
                                uint8* v,
-                               int width);
+                               ptrdiff_t width);
 
 #ifdef __cplusplus
 }