Desktop aura: Continue threading context through views.

ui/views/widget/widget.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_VIEWS_WIDGET_WIDGET_H_
 #define UI_VIEWS_WIDGET_WIDGET_H_
 
 #include <set>
 #include <stack>
 #include <vector>
@@ skipping 127 matching lines @@
       WIDGET_OWNS_NATIVE_WIDGET
     };
 
     InitParams();
     explicit InitParams(Type type);
 
     // If |parent_widget| is non-null, its native view is returned, otherwise
     // |parent| is returned.
     gfx::NativeView GetParent() const;
 
+    // Will return the first of the following that isn't NULL: the native view,
+    // |parent|, |context|.
+    gfx::NativeView GetContext() const;
+
     Type type;
     // If NULL, a default implementation will be constructed.
     WidgetDelegate* delegate;
     bool child;
     bool transient;
     // If true, the widget may be fully or partially transparent.  If false,
     // we can perform optimizations based on the widget being fully opaque.
     // For window widgets, defaults to ViewsDelegate::UseTransparentWindows().
     // Defaults to false for non-window widgets.
     bool transparent;
@@ skipping 26 matching lines @@
     NativeWidget* native_widget;
     // Aura-only. Provides a DesktopRootWindowHost implementation to use instead
     // of the default one.
     // TODO(beng): Figure out if there's a better way to expose this, e.g. get
     // rid of NW subclasses and do this all via message handling.
     DesktopRootWindowHost* desktop_root_window_host;
     bool top_level;
     // Only used by NativeWidgetAura. Specifies the type of layer for the
     // aura::Window. Default is LAYER_TEXTURED.
     ui::LayerType layer_type;
-    // Only used by Aura. Provides additional context (generally a RootWindow)
-    // during creation to allow the widget to determine which desktop type it
-    // will belong to. NULL is not allowed if you are using aura.
+    // Only used by Aura. Provides a context window whose RootWindow we be
+    // consulted during widget creation to determine where in the Window
+    // hierarchy this widget should be placed. (This is separate from |parent|;
+    // if you pass a RootWindow to |parent|, your window will be parented to
+    // |parent|. If you pass a RootWindow to |context|, we ask that RootWindow
+    // where it wants your window placed.) NULL is not allowed if you are using
+    // aura.
     gfx::NativeView context;
   };
 
   Widget();
   virtual ~Widget();
 
   // Creates a decorated window Widget with the specified properties.
   static Widget* CreateWindow(WidgetDelegate* delegate);
   static Widget* CreateWindowWithParent(WidgetDelegate* delegate,
                                         gfx::NativeWindow parent);
@@ skipping 604 matching lines @@
 
   // Is |root_layers_| out of date?
   bool root_layers_dirty_;
 
   DISALLOW_COPY_AND_ASSIGN(Widget);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_WIDGET_H_