V4L2VDA: do not allocate input buffers in GPU child thread.

media/gpu/v4l2_video_decode_accelerator.h

Index: media/gpu/v4l2_video_decode_accelerator.h
diff --git a/media/gpu/v4l2_video_decode_accelerator.h b/media/gpu/v4l2_video_decode_accelerator.h
index 208fa70b94df9201859e7a3e3dd18859a4cb18e4..8e31c0ce7dc6cb984b906311bbb129a17a6ab98c 100644
--- a/media/gpu/v4l2_video_decode_accelerator.h
+++ b/media/gpu/v4l2_video_decode_accelerator.h
@@ -202,6 +202,9 @@ class MEDIA_GPU_EXPORT V4L2VideoDecodeAccelerator
   // Decoding tasks, to be run on decode_thread_.
   //
 
+  // Task to finish initialization on decoder_thread_.
+  void InitializeTask();
+
   // Enqueue a BitstreamBuffer to decode.  This will enqueue a buffer to the
   // decoder_input_queue_, then queue a DecodeBufferTask() to actually decode
   // the buffer.