Update libwebp to 0.4.0

third_party/libwebp/utils/huffman.h

Index: third_party/libwebp/utils/huffman.h
diff --git a/third_party/libwebp/utils/huffman.h b/third_party/libwebp/utils/huffman.h
index 83a517ee60dd1421cbeebf488e6684dcad7e8242..e8afd27f24468a931d8d94058d8c71e5f42f7108 100644
--- a/third_party/libwebp/utils/huffman.h
+++ b/third_party/libwebp/utils/huffman.h
@@ -17,7 +17,7 @@
 #include <assert.h>
 #include "../webp/types.h"
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 extern "C" {
 #endif
 
@@ -28,17 +28,24 @@ typedef struct {
 } HuffmanTreeNode;
 
 // Huffman Tree.
+#define HUFF_LUT_BITS 7
+#define HUFF_LUT (1U << HUFF_LUT_BITS)
 typedef struct HuffmanTree HuffmanTree;
 struct HuffmanTree {
+  // Fast lookup for short bit lengths.
+  uint8_t lut_bits_[HUFF_LUT];
+  int16_t lut_symbol_[HUFF_LUT];
+  int16_t lut_jump_[HUFF_LUT];
+  // Complete tree for lookups.
   HuffmanTreeNode* root_;   // all the nodes, starting at root.
   int max_nodes_;           // max number of nodes
   int num_nodes_;           // number of currently occupied nodes
 };
 
-// Returns true if the given node is a leaf of the Huffman tree.
-static WEBP_INLINE int HuffmanTreeNodeIsLeaf(
+// Returns true if the given node is not a leaf of the Huffman tree.
+static WEBP_INLINE int HuffmanTreeNodeIsNotLeaf(
     const HuffmanTreeNode* const node) {
-  return (node->children_ == 0);
+  return node->children_;
 }
 
 // Go down one level. Most critical function. 'right_child' must be 0 or 1.
@@ -73,7 +80,7 @@ int HuffmanCodeLengthsToCodes(const int* const code_lengths,
                               int code_lengths_size, int* const huff_codes);
 
 
-#if defined(__cplusplus) || defined(c_plusplus)
+#ifdef __cplusplus
 }    // extern "C"
 #endif