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

chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc

Index: chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc
diff --git a/chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc b/chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc
index caae453fecac4718cddc0f85445de86c9dd05b42..dd62b1d2394142d704a378e2983c833b2177189b 100644
--- a/chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc
+++ b/chrome/browser/ui/views/tab_modal_confirm_dialog_views.cc
@@ -32,8 +32,10 @@ TabModalConfirmDialogViews::TabModalConfirmDialogViews(
     content::WebContents* web_contents)
     : delegate_(delegate),
       message_box_view_(new views::MessageBoxView(
-          views::MessageBoxView::InitParams(delegate->GetMessage()))) {
-  delegate_->set_window(ConstrainedWindowViews::Create(web_contents, this));
+          views::MessageBoxView::InitParams(delegate->GetMessage()))),
+      dialog_(NULL) {
+  dialog_ = ConstrainedWindowViews::Create(web_contents, this);
+  delegate_->set_close_delegate(this);
 }
 
 TabModalConfirmDialogViews::~TabModalConfirmDialogViews() {
@@ -47,6 +49,10 @@ void TabModalConfirmDialogViews::CancelTabModalDialog() {
   GetDialogClientView()->CancelWindow();
 }
 
+void TabModalConfirmDialogViews::CloseDialog() {
+  dialog_->CloseWebContentsModalDialog();
+}
+
 //////////////////////////////////////////////////////////////////////////////
 // TabModalConfirmDialogViews, views::DialogDelegate implementation: