Factor out uses of the WebContentsModalDialog interface from platform-independent code

chrome/browser/ui/views/tab_modal_confirm_dialog_views.h

Index: chrome/browser/ui/views/tab_modal_confirm_dialog_views.h
diff --git a/chrome/browser/ui/views/tab_modal_confirm_dialog_views.h b/chrome/browser/ui/views/tab_modal_confirm_dialog_views.h
index e00df831897c33889fb94cab9e282121bd66fcc3..0fd23d1695f500d9fa423ee3656f39b6fb0564d3 100644
--- a/chrome/browser/ui/views/tab_modal_confirm_dialog_views.h
+++ b/chrome/browser/ui/views/tab_modal_confirm_dialog_views.h
@@ -11,6 +11,8 @@
 #include "ui/gfx/native_widget_types.h"
 #include "ui/views/window/dialog_delegate.h"
 
+class ConstrainedWindowViews;
+
 namespace content {
 class WebContents;
 }
@@ -50,11 +52,16 @@ class TabModalConfirmDialogViews : public TabModalConfirmDialog,
   virtual void AcceptTabModalDialog() OVERRIDE;
   virtual void CancelTabModalDialog() OVERRIDE;
 
+  // TabModalConfirmDialogCloseDelegate:
+  virtual void CloseDialog() OVERRIDE;
+
   scoped_ptr<TabModalConfirmDialogDelegate> delegate_;
 
   // The message box view whose commands we handle.
   views::MessageBoxView* message_box_view_;
 
+  ConstrainedWindowViews* dialog_;
+
   DISALLOW_COPY_AND_ASSIGN(TabModalConfirmDialogViews);
 };