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 f0a5626d2d41ae6b7600574a021e975161bc8d5b..382625a0cbf85a3ea52dd6ca8b411cf18b32dbbf 100644
--- a/media/video/video_decode_accelerator.cc
+++ b/media/video/video_decode_accelerator.cc
@@ -40,13 +40,23 @@ 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_UNKNOWN;
+}
+
 VideoDecodeAccelerator::SupportedProfile::SupportedProfile()
     : profile(media::VIDEO_CODEC_PROFILE_UNKNOWN), encrypted_only(false) {}