M420ToARGB use NV12ToARGB_Neon internals

BUG=138
TESTED=sudo LIBYUV_REPEAT=1000 nice --5 ./libyuv_unittest --gtest_filter=*M420* | sed 's/\(.*(\)\([0-9]*\)\( ms)\)/\2 - \1\2\3/g' | sort -rn | grep ms
Review URL: https://webrtc-codereview.appspot.com/935009

git-svn-id: http://libyuv.googlecode.com/svn/trunk@456 16f28f9a-4ce2-e073-06de-1de4eb20be90

source/convert_argb.cc

@@ -675,6 +675,13 @@ int M420ToARGB(const uint8* src_m420, int src_stride_m420,
       }
     }
   }
+#elif defined(HAS_NV12TOARGBROW_NEON)
+  if (TestCpuFlag(kCpuHasNEON) && width >= 8) {
+    NV12ToARGBRow = NV12ToARGBRow_Any_NEON;
+    if (IS_ALIGNED(width, 8)) {
+      NV12ToARGBRow = NV12ToARGBRow_NEON;
+    }
+  }
 #endif
 
   for (int y = 0; y < height - 1; y += 2) {