FakeVideoCaptureDevice: add support for capturing into Dma-Bufs using VGEM in CrOs

media/video/capture/video_capture_device.cc

Index: media/video/capture/video_capture_device.cc
diff --git a/media/video/capture/video_capture_device.cc b/media/video/capture/video_capture_device.cc
index 44442c49a502c1edaa6cee21b4b0ecbb18cc12df..26314b78efc2a0a670ca8032c233a71b872fb072 100644
--- a/media/video/capture/video_capture_device.cc
+++ b/media/video/capture/video_capture_device.cc
@@ -130,6 +130,10 @@ const char* VideoCaptureDevice::Name::GetCaptureApiTypeString() const {
 
 VideoCaptureDevice::Client::Buffer::~Buffer() {}
 
+base::PlatformFile VideoCaptureDevice::Client::Buffer::AsPlatformFile() {
+  return base::PlatformFile();
+}
+
 VideoCaptureDevice::~VideoCaptureDevice() {}
 
 int VideoCaptureDevice::GetPowerLineFrequencyForLocation() const {