Have SkWuffsCodec get workbuf_len from decoder

Getting it from the image_config is deprecated. There may be more than
one implementation of decoding any given compressed image format.

Bug: skia:8235
Change-Id: I17cb746467635c073c5bc55946b2bad4f067b1bf
Reviewed-on: https://skia-review.googlesource.com/c/183540
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
diff --git a/src/codec/SkWuffsCodec.cpp b/src/codec/SkWuffsCodec.cpp
index 5540672..a987dd4 100644
--- a/src/codec/SkWuffsCodec.cpp
+++ b/src/codec/SkWuffsCodec.cpp
@@ -897,7 +897,7 @@
         return nullptr;
     }
 
-    uint64_t workbuf_len = imgcfg.workbuf_len().max_incl;
+    uint64_t workbuf_len = wuffs_gif__decoder__workbuf_len(decoder.get()).max_incl;
     void*    workbuf_ptr_raw = workbuf_len <= SIZE_MAX ? sk_malloc_canfail(workbuf_len) : nullptr;
     if (!workbuf_ptr_raw) {
         *result = SkCodec::kInternalError;