Generalize layer mirroring for phantom windows

ui/views/cocoa/bridged_native_widget.mm

Index: ui/views/cocoa/bridged_native_widget.mm
diff --git a/ui/views/cocoa/bridged_native_widget.mm b/ui/views/cocoa/bridged_native_widget.mm
index c468ce88044fe01bb7e77e61f44678e734073375..ce3731d026165eb42ef39e0b00bafe6953e2fcf9 100644
--- a/ui/views/cocoa/bridged_native_widget.mm
+++ b/ui/views/cocoa/bridged_native_widget.mm
@@ -12,6 +12,7 @@
 #import "base/mac/foundation_util.h"
 #include "base/mac/mac_util.h"
 #import "base/mac/sdk_forward_declarations.h"
+#include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "ui/accelerated_widget_mac/window_resize_helper_mac.h"
 #import "ui/base/cocoa/constrained_window/constrained_window_animation.h"
@@ -962,7 +963,7 @@ void BridgedNativeWidget::CreateLayer(ui::LayerType layer_type,
   CreateCompositor();
   DCHECK(compositor_);
 
-  SetLayer(new ui::Layer(layer_type));
+  SetLayer(base::MakeUnique<ui::Layer>(layer_type));
   // Note, except for controls, this will set the layer to be hidden, since it
   // is only called during Init().
   layer()->SetVisible(window_visible_);