Update libwebp to 0.4.0

third_party/libwebp/utils/quant_levels.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.
 // -----------------------------------------------------------------------------
 //
 // Quantize levels for specified number of quantization-levels ([2, 256]).
 // Min and max values are preserved (usual 0 and 255 for alpha plane).
 //
 // Author: Skal (pascal.massimino@gmail.com)
 
 #include <assert.h>
 
 #include "./quant_levels.h"
 
-#if defined(__cplusplus) || defined(c_plusplus)
-extern "C" {
-#endif
-
 #define NUM_SYMBOLS     256
 
 #define MAX_ITER  6             // Maximum number of convergence steps.
 #define ERROR_THRESHOLD 1e-4    // MSE stopping criterion.
 
 // -----------------------------------------------------------------------------
 // Quantize levels.
 
 int QuantizeLevels(uint8_t* const data, int width, int height,
                    int num_levels, uint64_t* const sse) {
@@ skipping 102 matching lines @@
       data[n] = map[data[n]];
     }
   }
  End:
   // Store sum of squared error if needed.
   if (sse != NULL) *sse = (uint64_t)err;
 
   return 1;
 }
 
-#if defined(__cplusplus) || defined(c_plusplus)
-}    // extern "C"
-#endif