Fix double mapoffset application in PipeWire video capture

mmap() with mapoffset as the file offset already returns a pointer to
the data at that offset, so passing it again to SPA_MEMBER was reading
mapoffset bytes past the mapped region. Also queue the buffer back to
PipeWire before returning on mmap failure to avoid leaking it.

Bug: chromium:505647674
Change-Id: Iba306e80b008e71b420f15e74db67b1496ddc403
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/466361
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Jan Grulich <grulja@gmail.com>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47562}

modules/video_capture/linux/video_capture_pipewire.cc

diff --git a/modules/video_capture/linux/video_capture_pipewire.cc b/modules/video_capture/linux/video_capture_pipewire.cc
index ca35498..c83867e 100644
--- a/modules/video_capture/linux/video_capture_pipewire.cc
+++ b/modules/video_capture/linux/video_capture_pipewire.cc
@@ -490,12 +490,12 @@
       if (!frame) {
         RTC_LOG(LS_ERROR) << "Failed to mmap the memory: "
                           << std::strerror(errno);
+        pw_stream_queue_buffer(stream_, buffer);
         return;
       }
 
-      IncomingFrame(
-          SPA_MEMBER(frame.get(), spaBuffer->datas[0].mapoffset, uint8_t),
-          spaBuffer->datas[0].chunk->size, configured_capability_);
+      IncomingFrame(frame.get(), spaBuffer->datas[0].chunk->size,
+                    configured_capability_);
     } else {  // SPA_DATA_MemPtr
       IncomingFrame(static_cast<uint8_t*>(spaBuffer->datas[0].data),
                     spaBuffer->datas[0].chunk->size, configured_capability_);