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

content/public/gpu/gpu_video_decode_accelerator_factory.h

Index: content/public/gpu/gpu_video_decode_accelerator_factory.h
diff --git a/content/public/gpu/gpu_video_decode_accelerator_factory.h b/content/public/gpu/gpu_video_decode_accelerator_factory.h
index 313306bdd36af0d05b4f74cf2af26e47130afa07..6dff49f66e0b4a50401aef4b1ad534be62cebead 100644
--- a/content/public/gpu/gpu_video_decode_accelerator_factory.h
+++ b/content/public/gpu/gpu_video_decode_accelerator_factory.h
@@ -70,6 +70,13 @@ class CONTENT_EXPORT GpuVideoDecodeAcceleratorFactory {
       const BindGLImageCallback& bind_image_cb,
       const GetGLES2DecoderCallback& get_gles2_decoder_cb);
 
+  // Create a factory capable of producing VDA instances for current platform
+  // with no GL support.
+  // A factory created with this method will only be able to produce VDAs with
+  // no ability to call GL functions/access GL state. This also implies no
+  // ability to decode into textures provided by the client.
+  static std::unique_ptr<GpuVideoDecodeAcceleratorFactory> CreateWithNoGL();
+
   // Return decoder capabilities supported on the current platform.
   static gpu::VideoDecodeAcceleratorCapabilities GetDecoderCapabilities();