Generalize layer mirroring for phantom windows

content/browser/renderer_host/delegated_frame_host.cc

Index: content/browser/renderer_host/delegated_frame_host.cc
diff --git a/content/browser/renderer_host/delegated_frame_host.cc b/content/browser/renderer_host/delegated_frame_host.cc
index 268d45bd683a19b8e912a22c11363739bb656219..ca282ff89f521ffdd5086aaf76d8bbb729c7172c 100644
--- a/content/browser/renderer_host/delegated_frame_host.cc
+++ b/content/browser/renderer_host/delegated_frame_host.cc
@@ -897,10 +897,14 @@ void DelegatedFrameHost::OnLayerRecreated(ui::Layer* old_layer,
   // The new_layer is the one that will be used by our Window, so that's the one
   // that should keep our frame. old_layer will be returned to the
   // RecreateLayer caller, and should have a copy.
+  OnLayerMirrored(new_layer);
+}
+
+void DelegatedFrameHost::OnLayerMirrored(ui::Layer* mirror) {
   if (!surface_id_.is_null()) {
     ImageTransportFactory* factory = ImageTransportFactory::GetInstance();
     cc::SurfaceManager* manager = factory->GetSurfaceManager();
-    new_layer->SetShowSurface(
+    mirror->SetShowSurface(
         surface_id_, base::Bind(&SatisfyCallback, base::Unretained(manager)),
         base::Bind(&RequireCallback, base::Unretained(manager)),
         current_surface_size_, current_scale_factor_,