call base.BeginDraw we dont need our own session class.

src/Windows/Avalonia.Win32/Composition/CompositionHost.cs

@@ -69,58 +69,8 @@ namespace Avalonia.Win32
 
                 var restoreContext = _context.MakeCurrent(surface);
 
-                return new Session(_display, _context, surface, _info, l, restoreContext, () => { _surfaceInterop.EndDraw(); }, true);
+                return base.BeginDraw(surface, _info, () => { _surfaceInterop.EndDraw(); }, true);
             }
-
-            public override void Dispose()
-            {
-                _surfaceInterop.EndDraw();
-                base.Dispose();
-            }
-        }
-
-        class Session : IGlPlatformSurfaceRenderingSession
-        {
-            private readonly EglContext _context;
-            private readonly EglSurface _glSurface;
-            private readonly EglGlPlatformSurfaceBase.IEglWindowGlPlatformSurfaceInfo _info;
-            private readonly EglDisplay _display;
-            private readonly IDisposable _lock;
-            private readonly IDisposable _restoreContext;
-            private readonly Action _onFinish;
-
-
-            public Session(EglDisplay display, EglContext context,
-                EglSurface glSurface, EglGlPlatformSurfaceBase.IEglWindowGlPlatformSurfaceInfo info,
-                IDisposable @lock, IDisposable restoreContext, Action onFinish, bool isYFlipped)
-            {
-                IsYFlipped = isYFlipped;
-                _context = context;
-                _display = display;
-                _glSurface = glSurface;
-                _info = info;
-                _lock = @lock;
-                _restoreContext = restoreContext;
-                _onFinish = onFinish;
-            }
-
-            public void Dispose()
-            {
-                _context.GlInterface.Flush();
-                _display.EglInterface.WaitGL();
-                _glSurface.SwapBuffers();
-                _display.EglInterface.WaitClient();
-                _display.EglInterface.WaitGL();
-                _display.EglInterface.WaitNative(EglConsts.EGL_CORE_NATIVE_ENGINE);
-                _restoreContext.Dispose();
-                _lock.Dispose();
-                _onFinish?.Invoke();
-            }
-
-            public IGlContext Context => _context;
-            public PixelSize Size => _info.Size;
-            public double Scaling => _info.Scaling;
-            public bool IsYFlipped { get; }
         }
     }