Support external buffer import in VDA interface and add a V4L2SVDA impl.

media/video/video_decode_accelerator.cc

Index: media/video/video_decode_accelerator.cc
diff --git a/media/video/video_decode_accelerator.cc b/media/video/video_decode_accelerator.cc
index fa7138b6e59f133ee599ea7feeb4d51cfbf55dd0..4f36546dd375dd8cf7c81ce0f2a208d9e6b6340f 100644
--- a/media/video/video_decode_accelerator.cc
+++ b/media/video/video_decode_accelerator.cc
@@ -39,13 +39,23 @@ bool VideoDecodeAccelerator::TryToSetupDecodeOnSeparateThread(
     const scoped_refptr<base::SingleThreadTaskRunner>& decode_task_runner) {
   // Implementations in the process that VDA runs in must override this.
   LOG(FATAL) << "This may only be called in the same process as VDA impl.";
-  return false;  // not reached
+  return false;
+}
+
+void VideoDecodeAccelerator::ImportBufferForPicture(
+    int32_t picture_buffer_id,
+    const std::vector<gfx::GpuMemoryBufferHandle>& gpu_memory_buffer_handles) {
+  NOTREACHED() << "Buffer import not supported.";
 }
 
 GLenum VideoDecodeAccelerator::GetSurfaceInternalFormat() const {
   return GL_RGBA;
 }
 
+VideoPixelFormat VideoDecodeAccelerator::GetOutputFormat() const {
+  return PIXEL_FORMAT_ARGB;
+}
+
 VideoDecodeAccelerator::SupportedProfile::SupportedProfile()
     : profile(media::VIDEO_CODEC_PROFILE_UNKNOWN) {}