Treat YU12 as an alias for I420. Simplify setting of inv_crop_height.

source/convert_to_argb.cc

 /*
  *  Copyright 2011 The LibYuv Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS. All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 158 matching lines @@
                      crop_width, inv_crop_height);
       break;
     case FOURCC_M420:
       src = sample + (src_width * crop_y) * 12 / 8 + crop_x;
       r = M420ToARGB(src, src_width,
                      crop_argb, argb_stride,
                      crop_width, inv_crop_height);
       break;
     // Triplanar formats
     case FOURCC_I420:
-    case FOURCC_YU12:
     case FOURCC_YV12: {
       const uint8* src_y = sample + (src_width * crop_y + crop_x);
       const uint8* src_u;
       const uint8* src_v;
       int halfwidth = (src_width + 1) / 2;
       int halfheight = (abs_src_height + 1) / 2;
       if (format == FOURCC_YV12) {
         src_v = sample + src_width * abs_src_height +
             (halfwidth * crop_y + crop_x) / 2;
         src_u = sample + src_width * abs_src_height +
@@ skipping 107 matching lines @@
     free(rotate_buffer);
   }
 
   return r;
 }
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif