Generalize layer mirroring for phantom windows

ash/common/wm/forwarding_layer_delegate.cc

-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "ash/common/wm/forwarding_layer_delegate.h"
-
-#include "ash/common/wm_window.h"
-#include "ui/compositor/layer.h"
-#include "ui/compositor/layer_owner.h"
-
-namespace ash {
-namespace wm {
-
-ForwardingLayerDelegate::ForwardingLayerDelegate(ui::Layer* new_layer,
-                                                 ui::Layer* original_layer)
-    : client_layer_(new_layer),
-      original_layer_(original_layer),
-      scoped_observer_(this) {
-  scoped_observer_.Add(original_layer);
-}
-
-ForwardingLayerDelegate::~ForwardingLayerDelegate() {}
-
-void ForwardingLayerDelegate::OnPaintLayer(const ui::PaintContext& context) {
-  if (original_layer_ && original_layer_->delegate())
-    original_layer_->delegate()->OnPaintLayer(context);
-}
-
-void ForwardingLayerDelegate::OnDelegatedFrameDamage(
-    const gfx::Rect& damage_rect_in_dip) {}
-
-void ForwardingLayerDelegate::OnDeviceScaleFactorChanged(
-    float device_scale_factor) {
-  // Don't tell the original delegate about device scale factor change
-  // on cloned layer because the original layer is still on the same display.
-}
-
-void ForwardingLayerDelegate::DidPaintLayer(ui::Layer* layer,
-                                            const gfx::Rect& rect) {
-  client_layer_->SchedulePaint(rect);
-}
-
-void ForwardingLayerDelegate::SurfaceChanged(ui::Layer* layer) {
-  // This will delete the old layer and any descendants.
-  ui::LayerOwner old_client;
-  old_client.SetLayer(client_layer_);
-
-  ui::LayerOwner* owner = layer->owner();
-  // The layer recreation step isn't recursive, but layers with surfaces don't
-  // tend to have children anyway. We may end up missing some children, but we
-  // can also reach that state if layers are ever added or removed.
-  // TODO(estade): address this if it ever becomes a practical issue.
-  std::unique_ptr<ui::Layer> recreated = owner->RecreateLayer();
-  client_layer_ = recreated.get();
-  old_client.layer()->parent()->Add(recreated.release());
-  old_client.layer()->parent()->Remove(old_client.layer());
-
-  scoped_observer_.Remove(original_layer_);
-  original_layer_ = owner->layer();
-  scoped_observer_.Add(original_layer_);
-}
-
-void ForwardingLayerDelegate::LayerDestroyed(ui::Layer* layer) {
-  original_layer_ = nullptr;
-  scoped_observer_.Remove(layer);
-}
-
-}  // namespace wm
-}  // namespace ash