Update libwebp to 0.4.0

third_party/libwebp/utils/quant_levels_dec.h

Index: third_party/libwebp/utils/quant_levels_dec.h
diff --git a/third_party/libwebp/utils/quant_levels_dec.h b/third_party/libwebp/utils/quant_levels_dec.h
index 58910676508bb7370b3ecec1d055020548636625..0288383aeb7498f18a0ae0974a1e73035e225a94 100644
--- a/third_party/libwebp/utils/quant_levels_dec.h
+++ b/third_party/libwebp/utils/quant_levels_dec.h
@@ -16,16 +16,18 @@
 
 #include "../webp/types.h"
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 extern "C" {
 #endif
 
-// Apply post-processing to input 'data' of size 'width'x'height' assuming
-// that the source was quantized to a reduced number of levels.
+// Apply post-processing to input 'data' of size 'width'x'height' assuming that
+// the source was quantized to a reduced number of levels. The post-processing
+// will be applied to 'num_rows' rows of 'data' starting from 'row'.
 // Returns false in case of error (data is NULL, invalid parameters, ...).
-int DequantizeLevels(uint8_t* const data, int width, int height);
+int DequantizeLevels(uint8_t* const data, int width, int height,
+                     int row, int num_rows);
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 }    // extern "C"
 #endif