Update libwebp to 0.4.0

third_party/libwebp/enc/layer.c

 // Copyright 2011 Google Inc. All Rights Reserved.
 //
 // Use of this source code is governed by a BSD-style license
 // that can be found in the COPYING 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.
 // -----------------------------------------------------------------------------
 //
 // Enhancement layer (for YUV444/422)
 //
 // Author: Skal (pascal.massimino@gmail.com)
 
 #include <stdlib.h>
 
 #include "./vp8enci.h"
 
-#if defined(__cplusplus) || defined(c_plusplus)
-extern "C" {
-#endif
-
 //------------------------------------------------------------------------------
 
 void VP8EncInitLayer(VP8Encoder* const enc) {
   enc->use_layer_ = (enc->pic_->u0 != NULL);
   enc->layer_data_size_ = 0;
   enc->layer_data_ = NULL;
   if (enc->use_layer_) {
     VP8BitWriterInit(&enc->layer_bw_, enc->mb_w_ * enc->mb_h_ * 3);
   }
 }
 
 void VP8EncCodeLayerBlock(VP8EncIterator* it) {
   (void)it;   // remove a warning
 }
 
 int VP8EncFinishLayer(VP8Encoder* const enc) {
   if (enc->use_layer_) {
     enc->layer_data_ = VP8BitWriterFinish(&enc->layer_bw_);
     enc->layer_data_size_ = VP8BitWriterSize(&enc->layer_bw_);
   }
   return 1;
 }
 
 void VP8EncDeleteLayer(VP8Encoder* enc) {
   free(enc->layer_data_);
 }
 
-#if defined(__cplusplus) || defined(c_plusplus)
-}    // extern "C"
-#endif