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..dc3baf295baa3013bb7dcc761c9bbce6a4564ed6 100644
--- a/media/gpu/v4l2_video_decode_accelerator.h
+++ b/media/gpu/v4l2_video_decode_accelerator.h
@@ -136,7 +136,7 @@ class MEDIA_GPU_EXPORT V4L2VideoDecodeAccelerator
   // Internal state of the decoder.
   enum State {
     kUninitialized,  // Initialize() not yet called.
-    kInitialized,    // Initialize() returned true; ready to start decoding.
+    kInitialized,    // InitializeTask() succeeds; ready to start decoding.
     kDecoding,       // DecodeBufferInitial() successful; decoding frames.
     kResetting,      // Presently resetting.
     // Performing resolution change and waiting for image processor to return
@@ -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.