Reimplement NV21ToARGB to allow different color matrix.

source/row_common.cc

Index: source/row_common.cc
diff --git a/source/row_common.cc b/source/row_common.cc
index b810849d9b9a244233dd845892ae3f06de195c46..0b236e72ea5813abfea22a6475afaba0d9f97312 100644
--- a/source/row_common.cc
+++ b/source/row_common.cc
@@ -1663,6 +1663,30 @@ void NV12ToARGBRow_C(const uint8* src_y,
   }
 }
 
+void NV21ToARGBRow_C(const uint8* src_y,
+                     const uint8* src_vu,
+                     uint8* rgb_buf,
+                     struct YuvConstants* yuvconstants,
+                     int width) {
+  int x;
+  for (x = 0; x < width - 1; x += 2) {
+    YuvPixel(src_y[0], src_vu[1], src_vu[0],
+             rgb_buf + 0, rgb_buf + 1, rgb_buf + 2, yuvconstants);
+    rgb_buf[3] = 255;
+    YuvPixel(src_y[1], src_vu[1], src_vu[0],
+             rgb_buf + 4, rgb_buf + 5, rgb_buf + 6, yuvconstants);
+    rgb_buf[7] = 255;
+    src_y += 2;
+    src_vu += 2;
+    rgb_buf += 8;  // Advance 2 pixels.
+  }
+  if (width & 1) {
+    YuvPixel(src_y[0], src_vu[1], src_vu[0],
+             rgb_buf + 0, rgb_buf + 1, rgb_buf + 2, yuvconstants);
+    rgb_buf[3] = 255;
+  }
+}
+
 void NV12ToRGB565Row_C(const uint8* src_y,
                        const uint8* src_uv,
                        uint8* dst_rgb565,