media/gpu/v4l2vd: add missing checks and logs when queuing buffers

The queue statements on input buffers were not checked, which could lead
to errors going unnoticed and only being noticed later. Similarly an
error when queueing an output buffer should result in an error message.

BUG=None
TEST=video.DecodeAccel.h264 passes on Trogdor.

Change-Id: Ib96af994c34dadf63c827f0284a8c8a581c016b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2440327
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Fritz Koenig <frkoenig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813626}

media/gpu/v4l2/v4l2_video_decoder_backend_stateful.cc

@@ -213,7 +213,10 @@ void V4L2StatefulVideoDecoderBackend::DoDecodeWork() {
   }
 
   // The V4L2 input buffer contains a decodable entity, queue it.
-  std::move(*current_input_buffer_).QueueMMap();
+  if (!std::move(*current_input_buffer_).QueueMMap()) {
+    LOG(ERROR) << "Error while queuing input buffer!";
+    client_->OnBackendError();
+  }
   current_input_buffer_.reset();
 
   // If we can still progress on a decode request, do it.
@@ -297,8 +300,10 @@ void V4L2StatefulVideoDecoderBackend::EnqueueOutputBuffers() {
     if (no_buffer)
       break;
 
-    if (!ret)
+    if (!ret) {
+      LOG(ERROR) << "Error while queueing output buffer!";
       client_->OnBackendError();
+    }
   }
 
   DVLOGF(3) << output_queue_->QueuedBuffersCount() << "/"
@@ -428,7 +433,10 @@ bool V4L2StatefulVideoDecoderBackend::InitiateFlush(
 
   // Submit any pending input buffer at the time of flush.
   if (current_input_buffer_) {
-    std::move(*current_input_buffer_).QueueMMap();
+    if (!std::move(*current_input_buffer_).QueueMMap()) {
+      LOG(ERROR) << "Error while queuing input buffer!";
+      client_->OnBackendError();
+    }
     current_input_buffer_.reset();
   }