refactor: remove call DeprecatedLayoutImmediately()

It can never be nullptr, so return a reference

shell/browser/native_window_views.cc

@@ -469,13 +469,15 @@ void NativeWindowViews::SetGTKDarkThemeEnabled(bool use_dark_theme) {
 }
 
 void NativeWindowViews::SetContentView(views::View* view) {
-  if (content_view()) {
-    root_view_.GetMainView()->RemoveChildView(content_view());
-  }
+  auto& main_view = root_view_.main_view();
+
+  if (auto* prev_view = content_view())
+    main_view.RemoveChildView(prev_view);
+
   set_content_view(view);
   focused_view_ = view;
-  root_view_.GetMainView()->AddChildView(content_view());
-  root_view_.GetMainView()->DeprecatedLayoutImmediately();
+  main_view.AddChildView(view);
+  main_view.InvalidateLayout();
 }
 
 void NativeWindowViews::Close() {
@@ -1680,7 +1682,7 @@ std::u16string NativeWindowViews::GetWindowTitle() const {
 }
 
 views::View* NativeWindowViews::GetContentsView() {
-  return root_view_.GetMainView();
+  return &root_view_.main_view();
 }
 
 bool NativeWindowViews::ShouldDescendIntoChildForEventHandling(

shell/browser/ui/views/root_view.cc

@@ -38,9 +38,9 @@ RootView::RootView(NativeWindow* window)
   views::BoxLayout* layout =
       SetLayoutManager(std::make_unique<views::BoxLayout>(
           views::BoxLayout::Orientation::kVertical));
-  main_view_ = AddChildView(std::make_unique<views::View>());
-  main_view_->SetUseDefaultFillLayout(true);
-  layout->SetFlexForView(main_view_, 1);
+  AddChildView(&main_view_);
+  main_view_.SetUseDefaultFillLayout(true);
+  layout->SetFlexForView(&main_view_, 1);
 }
 
 RootView::~RootView() = default;

shell/browser/ui/views/root_view.h

@@ -46,7 +46,7 @@ class RootView : public views::View {
   void RegisterAcceleratorsWithFocusManager(ElectronMenuModel* menu_model);
   void UnregisterAcceleratorsWithFocusManager();
 
-  views::View* GetMainView() { return main_view_; }
+  [[nodiscard]] views::View& main_view() { return main_view_; }
 
   // views::View:
   gfx::Size GetMinimumSize() const override;
@@ -64,7 +64,7 @@ class RootView : public views::View {
   bool menu_bar_alt_pressed_ = false;
 
   // Main view area.
-  raw_ptr<views::View> main_view_;
+  views::View main_view_;
 
   // Map from accelerator to menu item's command id.
   accelerator_util::AcceleratorTable accelerator_table_;