views: add layout delegates

ui/views/view.h

Index: ui/views/view.h
diff --git a/ui/views/view.h b/ui/views/view.h
index 050548f0120ac7c90a3e5630966e5177208db8cf..8a32eccaf018e363ac63ebc1760c74d10e55863c 100644
--- a/ui/views/view.h
+++ b/ui/views/view.h
@@ -36,6 +36,7 @@
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/path.h"
+#include "ui/views/layout/layout_delegate.h"
 #include "ui/views/view_targeter.h"
 #include "ui/views/views_export.h"
 
@@ -73,6 +74,7 @@ class ContextMenuController;
 class DragController;
 class FocusManager;
 class FocusTraversable;
+class LayoutDelegate;
 class LayoutManager;
 class NativeViewAccessibility;
 class ScrollView;
@@ -396,6 +398,12 @@ class VIEWS_EXPORT View : public ui::LayerDelegate,
   LayoutManager* GetLayoutManager() const;
   void SetLayoutManager(LayoutManager* layout);
 
+  // Gets/Sets the Layout Delegate used by this view and its children / related
+  // views to compute spacing between and around elements. The LayoutDelegate is
+  // not owned by the View and should not be deleted.
+  LayoutDelegate* GetLayoutDelegate() const;
+  void SetLayoutDelegate(LayoutDelegate* delegate);
+
   // Adjust the layer's offset so that it snaps to the physical pixel boundary.
   // This has no effect if the view does not have an associated layer.
   void SnapLayerToPixelBoundary();
@@ -1511,6 +1519,9 @@ class VIEWS_EXPORT View : public ui::LayerDelegate,
   // Views. The default is absolute positioning according to bounds_.
   std::unique_ptr<LayoutManager> layout_manager_;
 
+  // The View's LayoutDelegate, if it has one.
+  LayoutDelegate* layout_delegate_ = nullptr;
+
   // Whether this View's layer should be snapped to the pixel boundary.
   bool snap_layer_to_pixel_boundary_;