libwebp: update to 0.4.1

third_party/libwebp/webp/decode.h

Index: third_party/libwebp/webp/decode.h
diff --git a/third_party/libwebp/webp/decode.h b/third_party/libwebp/webp/decode.h
index 0c3b62e215b8d726d55a35a27adfb564b15a4e64..36c27c3775b9c53aac4760a24c2371254dcbf8b6 100644
--- a/third_party/libwebp/webp/decode.h
+++ b/third_party/libwebp/webp/decode.h
@@ -442,11 +442,19 @@ struct WebPDecoderOptions {
   int scaled_width, scaled_height;    // final resolution
   int use_threads;                    // if true, use multi-threaded decoding
   int dithering_strength;             // dithering strength (0=Off, 100=full)
+#if WEBP_DECODER_ABI_VERSION > 0x0203
+  int flip;                           // flip output vertically
+  int alpha_dithering_strength;       // alpha dithering strength in [0..100]
+#endif
 
   // Unused for now:
   int force_rotation;                 // forced rotation (to be applied _last_)
   int no_enhancement;                 // if true, discard enhancement layer
+#if WEBP_DECODER_ABI_VERSION > 0x0203
+  uint32_t pad[3];                    // padding for later use
+#else
   uint32_t pad[5];                    // padding for later use
+#endif
 };
 
 // Main object storing the configuration for advanced decoding.