cc: Use the correct internal format for glCopyTexImage2D calls.

components/mus/surfaces/direct_output_surface.cc

Index: components/mus/surfaces/direct_output_surface.cc
diff --git a/components/mus/surfaces/direct_output_surface.cc b/components/mus/surfaces/direct_output_surface.cc
index 2f2b02f5c63a98725670af929d127ee8a9f81214..c4c3544230604e757e2c99026e47e16e9ea848e3 100644
--- a/components/mus/surfaces/direct_output_surface.cc
+++ b/components/mus/surfaces/direct_output_surface.cc
@@ -72,4 +72,10 @@ void DirectOutputSurface::SwapBuffers(cc::CompositorFrame* frame) {
   client_->DidSwapBuffers();
 }
 
+uint32_t DirectOutputSurface::GetFramebufferCopyTextureFormat() {
+  // TODO(danakj): What attributes are used for the default framebuffer here?
+  // Can it have alpha? SurfacesContextProvider doesn't take any attributes.
+  return GL_RGB;
+}
+
 }  // namespace mus