MacViews: Exploring removal of window-modal sheets.

components/constrained_window/constrained_window_views.cc

Index: components/constrained_window/constrained_window_views.cc
diff --git a/components/constrained_window/constrained_window_views.cc b/components/constrained_window/constrained_window_views.cc
index 3ed86ce06852a9da707d5868000e19a7103a8b7d..07c27e603a4586c91bfcfe5e82d9df8449155726 100644
--- a/components/constrained_window/constrained_window_views.cc
+++ b/components/constrained_window/constrained_window_views.cc
@@ -87,18 +87,6 @@ void UpdateModalDialogPosition(views::Widget* widget,
   if (widget->HasCapture())
     return;
 
-  views::Widget* host_widget =
-      views::Widget::GetWidgetForNativeView(dialog_host->GetHostView());
-
-  // If the host view is not backed by a Views::Widget, just update the widget
-  // size. This can happen on MacViews under the Cocoa browser where the window
-  // modal dialogs are displayed as sheets, and their position is managed by a
-  // ConstrainedWindowSheetController instance.
-  if (!host_widget) {
-    widget->SetSize(size);
-    return;
-  }
-
   gfx::Point position = dialog_host->GetDialogPosition(size);
   views::Border* border = widget->non_client_view()->frame_view()->border();
   // Border may be null during widget initialization.
@@ -109,7 +97,7 @@ void UpdateModalDialogPosition(views::Widget* widget,
   }
 
   if (widget->is_top_level())
-    position += host_widget->GetClientAreaBoundsInScreen().OffsetFromOrigin();
+    position += dialog_host->GetHostPosition().OffsetFromOrigin();
 
   widget->SetBounds(gfx::Rect(position, size));
 }
@@ -209,13 +197,6 @@ views::Widget* CreateBrowserModalDialogViews(views::DialogDelegate* dialog,
       views::DialogDelegate::CreateDialogWidget(dialog, nullptr, parent_view);
 
   bool requires_positioning = dialog->ShouldUseCustomFrame();
-
-#if defined(OS_MACOSX)
-  // On Mac, window modal dialogs are displayed as sheets, so their position is
-  // managed by the parent window.
-  requires_positioning = false;
-#endif
-
   if (!requires_positioning)
     return widget;
 
@@ -223,7 +204,14 @@ views::Widget* CreateBrowserModalDialogViews(views::DialogDelegate* dialog,
       parent ? constrained_window_views_client->GetModalDialogHost(parent)
              : nullptr;
   if (host) {
+#if !defined(OS_MACOSX)
+    // On Mac, the host view for tab-modal dialogs may differ from the host view
+    // for window-modal dialogs. There is only one ModalDialogHost per window,
+    // designed for tab-modal dialogs, but suitable for positioning window-
+    // modal dialogs as well.
+    // On other platforms, the gfx::NativeView should match.
     DCHECK_EQ(parent_view, host->GetHostView());
+#endif
     ModalDialogHostObserver* dialog_host_observer =
         new WidgetModalDialogHostObserverViews(
             host, widget, kWidgetModalDialogHostObserverViewsKey);