GPUVideoImage::GetAsSourceSurface() is heavy weight. It seems better to prevent to call it if possible.
The change handles only a case that CanvasTranslator is used, SurfaceDescriptor is RemoteDecoderVideoSubDescriptor::Tnull_t and OptimizeShadow is not used.
DrawTargetRecording::DrawSurfaceDescriptor() also holds layers::Image of SurfaceDescriptor. It is necessary to keep the Image alive in CanvasDrawEventRecorder until end of its usage in CanvasTranslator.
Differential Revision: https://phabricator.services.mozilla.com/D205677
9c96712d23