Use SPA_CHUNK_FLAG_CORRUPTED and SPA_META_HEADER_FLAG_CORRUPTED flags to

determine corrupted buffers or corrupted buffer data. We used to only
rely on compositors setting chunk->size, but this doesn't make sense for
dmabufs where they have to make up arbitrary values. It also looks this
is not reliable and can cause glitches as we end up processing corrupted buffers.

The original patch is rebased with `observer_` related code removed
since our branch does not have that.

See: https://webrtc-review.googlesource.com/c/src/+/349881
Co-Authored-By: Jan Grulich <grulja@gmail.com>

src/modules/desktop_capture/linux/wayland/shared_screencast_stream.cc

@@ -339,6 +339,16 @@ void SharedScreenCastStreamPrivate::OnStreamProcess(void* data) {
     return;
   }
 
+  struct spa_meta_header* header =
+      static_cast<spa_meta_header*>(spa_buffer_find_meta_data(
+          buffer->buffer, SPA_META_Header, sizeof(*header)));
+  if (header && (header->flags & SPA_META_HEADER_FLAG_CORRUPTED)) {
+    RTC_LOG(LS_INFO) << "Dropping corrupted buffer";
+    // Queue buffer for reuse; it will not be processed further.
+    pw_stream_queue_buffer(that->pw_stream_, buffer);
+    return;
+  }
+
   that->ProcessBuffer(buffer);
 
   pw_stream_queue_buffer(that->pw_stream_, buffer);
@@ -640,7 +650,14 @@ void SharedScreenCastStreamPrivate::ProcessBuffer(pw_buffer* buffer) {
     }
   }
 
-  if (spa_buffer->datas[0].chunk->size == 0) {
+  if (spa_buffer->datas[0].chunk->flags & SPA_CHUNK_FLAG_CORRUPTED) {
+    RTC_LOG(LS_INFO) << "Dropping buffer with corrupted or missing data";
+    return;
+  }
+
+  if (spa_buffer->datas[0].type == SPA_DATA_MemFd &&
+      spa_buffer->datas[0].chunk->size == 0) {
+    RTC_LOG(LS_INFO) << "Dropping buffer with empty data";
     return;
   }