simple_decoder.c: Silence MSVC data loss warning.

Change-Id: I138d7f62ac7e905642405e60a49ac3d282695e3f

examples/simple_decoder.c

@@ -134,7 +134,7 @@ int main(int argc, char **argv) {
     size_t frame_size = 0;
     const unsigned char *frame = vpx_video_reader_get_frame(reader,
                                                             &frame_size);
-    if (vpx_codec_decode(&codec, frame, frame_size, NULL, 0))
+    if (vpx_codec_decode(&codec, frame, (unsigned int)frame_size, NULL, 0))
       die_codec(&codec, "Failed to decode frame.");
 
     while ((img = vpx_codec_get_frame(&codec, &iter)) != NULL) {