V4L2SliceVDA: Fold DecodeSurface() into callers

Sister CL to crrev.com/c/1176279 -- this CL folds
V4L2SliceVideoDecodeAccelerator::DecodeSurface() into callers.

This simplifies extracting CreateSurface() and SurfaceReady()
into an interface, in turn allowing better unit testing.

Bug: 875005
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I07d6934316cac629b2e78e2e96b66a19864bdd9e
Reviewed-on: https://chromium-review.googlesource.com/1178322Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583796}

media/gpu/v4l2/v4l2_slice_video_decode_accelerator.cc

@@ -2580,7 +2580,8 @@ V4L2SliceVideoDecodeAccelerator::V4L2H264Accelerator::SubmitDecode(
 
   Reset();
 
-  v4l2_dec_->DecodeSurface(dec_surface);
+  DVLOGF(4) << "Submitting decode for surface: " << dec_surface->ToString();
+  v4l2_dec_->Enqueue(dec_surface);
   return Status::kOk;
 }
 
@@ -2815,7 +2816,8 @@ bool V4L2SliceVideoDecodeAccelerator::V4L2VP8Accelerator::SubmitDecode(
                               frame_hdr->frame_size))
     return false;
 
-  v4l2_dec_->DecodeSurface(dec_surface);
+  DVLOGF(4) << "Submitting decode for surface: " << dec_surface->ToString();
+  v4l2_dec_->Enqueue(dec_surface);
   return true;
 }
 
@@ -3118,7 +3120,8 @@ bool V4L2SliceVideoDecodeAccelerator::V4L2VP9Accelerator::SubmitDecode(
                               frame_hdr->frame_size))
     return false;
 
-  v4l2_dec_->DecodeSurface(dec_surface);
+  DVLOGF(4) << "Submitting decode for surface: " << dec_surface->ToString();
+  v4l2_dec_->Enqueue(dec_surface);
   return true;
 }
 
@@ -3202,14 +3205,6 @@ V4L2SliceVideoDecodeAccelerator::V4L2VP9Accelerator::
   return v4l2_pic->dec_surface();
 }
 
-void V4L2SliceVideoDecodeAccelerator::DecodeSurface(
-    const scoped_refptr<V4L2DecodeSurface>& dec_surface) {
-  DCHECK(decoder_thread_task_runner_->BelongsToCurrentThread());
-
-  DVLOGF(4) << "Submitting decode for surface: " << dec_surface->ToString();
-  Enqueue(dec_surface);
-}
-
 void V4L2SliceVideoDecodeAccelerator::SurfaceReady(
     int32_t bitstream_id,
     const scoped_refptr<V4L2DecodeSurface>& dec_surface) {

media/gpu/v4l2/v4l2_slice_video_decode_accelerator.h

@@ -134,10 +134,6 @@ class MEDIA_GPU_EXPORT V4L2SliceVideoDecodeAccelerator
   // Return true if the driver exposes V4L2 control |ctrl_id|, false otherwise.
   bool IsCtrlExposed(uint32_t ctrl_id);
 
-  // Decode of |dec_surface| is ready to be submitted and all codec-specific
-  // settings are set in hardware.
-  void DecodeSurface(const scoped_refptr<V4L2DecodeSurface>& dec_surface);
-
   // |dec_surface| is ready to be outputted once decode is finished.
   // This can be called before decode is actually done in hardware, and this
   // method is responsible for maintaining the ordering, i.e. the surfaces will