libwebp: update to 0.5.0

third_party/libwebp/utils/huffman_encode.h

Index: third_party/libwebp/utils/huffman_encode.h
diff --git a/third_party/libwebp/utils/huffman_encode.h b/third_party/libwebp/utils/huffman_encode.h
index 91aa18f464559f2bdf330bfc502d004800c7e296..a157165148514aea523a4b79405181c897a1ebfa 100644
--- a/third_party/libwebp/utils/huffman_encode.h
+++ b/third_party/libwebp/utils/huffman_encode.h
@@ -34,10 +34,9 @@ typedef struct {
 } HuffmanTreeCode;
 
 // Struct to represent the Huffman tree.
-// TODO(vikasa): Add comment for the fields of the Struct.
 typedef struct {
-  uint32_t total_count_;
-  int value_;
+  uint32_t total_count_;   // Symbol frequency.
+  int value_;              // Symbol value.
   int pool_index_left_;    // Index for the left sub-tree.
   int pool_index_right_;   // Index for the right sub-tree.
 } HuffmanTree;