views: Make view::Views::GetPreferredSize() const.

ui/views/layout/box_layout.h

Index: ui/views/layout/box_layout.h
diff --git a/ui/views/layout/box_layout.h b/ui/views/layout/box_layout.h
index 7670d8cb05e7bd15b59771b2e95c3ade65aabf84..be30560c59882cbeebb828e62250e0c3d5f21036 100644
--- a/ui/views/layout/box_layout.h
+++ b/ui/views/layout/box_layout.h
@@ -46,16 +46,18 @@ class VIEWS_EXPORT BoxLayout : public LayoutManager {
 
   // Overridden from views::LayoutManager:
   virtual void Layout(View* host) OVERRIDE;
-  virtual gfx::Size GetPreferredSize(View* host) OVERRIDE;
-  virtual int GetPreferredHeightForWidth(View* host, int width) OVERRIDE;
+  virtual gfx::Size GetPreferredSize(const View* host) const OVERRIDE;
+  virtual int GetPreferredHeightForWidth(const View* host,
+                                         int width) const OVERRIDE;
 
  private:
   // The preferred size for the dialog given the width of the child area.
-  gfx::Size GetPreferredSizeForChildWidth(View* host, int child_area_width);
+  gfx::Size GetPreferredSizeForChildWidth(const View* host,
+                                          int child_area_width) const;
 
   // The amount of space the layout requires in addition to any space for the
   // child views.
-  gfx::Size NonChildSize(View* host);
+  gfx::Size NonChildSize(const View* host) const;
 
   const Orientation orientation_;