libwebp: update to 0.4.1

third_party/libwebp/enc/vp8li.h

Index: third_party/libwebp/enc/vp8li.h
diff --git a/third_party/libwebp/enc/vp8li.h b/third_party/libwebp/enc/vp8li.h
index 96d6faed64d518b6ea4aacc916c411d00b07d5cf..6b6db127db3b92ae80faa28e8e59f36429d7a48b 100644
--- a/third_party/libwebp/enc/vp8li.h
+++ b/third_party/libwebp/enc/vp8li.h
@@ -14,6 +14,7 @@
 #ifndef WEBP_ENC_VP8LI_H_
 #define WEBP_ENC_VP8LI_H_
 
+#include "./backward_references.h"
 #include "./histogram.h"
 #include "../utils/bit_writer.h"
 #include "../webp/encode.h"
@@ -45,6 +46,12 @@ typedef struct {
   int use_palette_;
   int palette_size_;
   uint32_t palette_[MAX_PALETTE_SIZE];
+
+  // Some 'scratch' (potentially large) objects.
+  struct VP8LBackwardRefs refs_[2];  // Backward Refs array corresponding to
+                                     // LZ77 & RLE coding.
+  VP8LHashChain hash_chain_;         // HashChain data for constructing
+                                     // backward references.
 } VP8LEncoder;
 
 //------------------------------------------------------------------------------