Close web contents modal dialogs on content load start

chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.mm

Index: chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.mm
diff --git a/chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.mm b/chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.mm
index bdca853ebcf2ab6c9a6954bd61baca1fdf8d3a91..a006fe98eaf6c5d033aae0176d40ab2d42a0d9ae 100644
--- a/chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.mm
+++ b/chrome/browser/ui/cocoa/tab_modal_confirm_dialog_mac.mm
@@ -88,7 +88,7 @@ TabModalConfirmDialogMac::TabModalConfirmDialogMac(
       [[CustomConstrainedWindowSheet alloc]
           initWithCustomWindow:[alert_ window]]);
   window_.reset(new ConstrainedWindowMac(this, web_contents, sheet));
-  delegate_->set_close_delegate(this);
+  delegate_->set_operations_delegate(this);
 }
 
 TabModalConfirmDialogMac::~TabModalConfirmDialogMac() {
@@ -106,6 +106,10 @@ void TabModalConfirmDialogMac::CloseDialog() {
   window_->CloseWebContentsModalDialog();
 }
 
+void TabModalConfirmDialogMac::SetPreventCloseOnLoadStart(bool prevent) {
+  window_->SetPreventCloseOnLoadStart(prevent);
+}
+
 void TabModalConfirmDialogMac::OnConstrainedWindowClosed(
     ConstrainedWindowMac* window) {
   delete this;