libwebp: update to 0.4.2-rc2

third_party/libwebp/dec/vp8l.c

Index: third_party/libwebp/dec/vp8l.c
diff --git a/third_party/libwebp/dec/vp8l.c b/third_party/libwebp/dec/vp8l.c
index 81cf99fcac9f261da6e19c616e83cb177c2c9d62..a7e7e252238d4217d9988f01bc0ab5f6dd169362 100644
--- a/third_party/libwebp/dec/vp8l.c
+++ b/third_party/libwebp/dec/vp8l.c
@@ -234,6 +234,7 @@ static int ReadHuffmanCodeLengths(
 
  End:
   VP8LHuffmanTreeFree(&tree);
+  if (!ok) dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
   return ok;
 }
 
@@ -801,6 +802,7 @@ static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
       ok = 0;
       goto End;
     }
+    assert(br->eos_ == VP8LIsEndOfStream(br));
     ok = !br->error_;
     if (!ok) goto End;
   }
@@ -918,6 +920,7 @@ static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
       ok = 0;
       goto End;
     }
+    assert(br->eos_ == VP8LIsEndOfStream(br));
     ok = !br->error_;
     if (!ok) goto End;
   }
@@ -1354,6 +1357,10 @@ int VP8LDecodeImage(VP8LDecoder* const dec) {
   // Sanity checks.
   if (dec == NULL) return 0;
 
+  dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
+  assert(dec->hdr_.htree_groups_ != NULL);
+  assert(dec->hdr_.num_htree_groups_ > 0);
+
   io = dec->io_;
   assert(io != NULL);
   params = (WebPDecParams*)io->opaque;