# HG changeset patch
# User Timothy Nikkel <tnikkel@gmail.com>
# Date 1694697417 0
# Node ID cbbf997c33890c2c49d24079db83b6ebb74cd7d8
# Parent  1aa227e40ab488aa065fe035debff0615f67b1f1
Bug 1852749. Cherry-pick upstream libwebp fix. r=gfx-reviewers,lsalzman a=RyanVM

https://github.com/webmproject/libwebp/commit/95ea5226c870449522240ccff26f0b006037c520

Differential Revision: https://phabricator.services.mozilla.com/D188066

diff --git a/media/libwebp/src/dec/vp8l_dec.c b/media/libwebp/src/dec/vp8l_dec.c
--- a/media/libwebp/src/dec/vp8l_dec.c
+++ b/media/libwebp/src/dec/vp8l_dec.c
@@ -1236,19 +1236,30 @@ static int DecodeImageData(VP8LDecoder* 
       *src = VP8LColorCacheLookup(color_cache, key);
       goto AdvanceByOne;
     } else {  // Not reached
       goto Error;
     }
   }
 
   br->eos_ = VP8LIsEndOfStream(br);
-  if (dec->incremental_ && br->eos_ && src < src_end) {
+  // In incremental decoding:
+  // br->eos_ && src < src_last: if 'br' reached the end of the buffer and
+  // 'src_last' has not been reached yet, there is not enough data. 'dec' has to
+  // be reset until there is more data.
+  // !br->eos_ && src < src_last: this cannot happen as either the buffer is
+  // fully read, either enough has been read to reach 'src_last'.
+  // src >= src_last: 'src_last' is reached, all is fine. 'src' can actually go
+  // beyond 'src_last' in case the image is cropped and an LZ77 goes further.
+  // The buffer might have been enough or there is some left. 'br->eos_' does
+  // not matter.
+  assert(!dec->incremental_ || (br->eos_ && src < src_last) || src >= src_last);
+  if (dec->incremental_ && br->eos_ && src < src_last) {
     RestoreState(dec);
-  } else if (!br->eos_) {
+  } else if ((dec->incremental_ && src >= src_last) || !br->eos_) {
     // Process the remaining rows corresponding to last row-block.
     if (process_func != NULL) {
       process_func(dec, row > last_row ? last_row : row);
     }
     dec->status_ = VP8_STATUS_OK;
     dec->last_pixel_ = (int)(src - data);  // end-of-scan marker
   } else {
     // if not incremental, and we are past the end of buffer (eos_=1), then this