Fix a crash in the leak detection dialog on dismissing it.

CredentialLeakDialogView::Accept nulls the controller and creates a new tab.
During tab creation the framework may call some methods on the view to get its
title or buttons. Previosuly that led to a crash.
It doesn't matter what to return in those methods because the dialog is being
destroyed anyway.

Bug: 1039452,1036422
Change-Id: I985b7e79ac78431e216d3f27de001683846a29b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1991563Reviewed-by: Friedrich [CET] <fhorschig@chromium.org>
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729395}

chrome/browser/ui/views/passwords/credential_leak_dialog_view.cc

@@ -138,7 +138,9 @@ bool CredentialLeakDialogView::Close() {
 }
 
 int CredentialLeakDialogView::GetDialogButtons() const {
-  return controller_->ShouldShowCancelButton()
+  // |controller_| can be nullptr when the framework calls this method after a
+  // button click.
+  return controller_ && controller_->ShouldShowCancelButton()
              ? ui::DIALOG_BUTTON_OK | ui::DIALOG_BUTTON_CANCEL
              : ui::DIALOG_BUTTON_OK;
 }
@@ -153,7 +155,9 @@ void CredentialLeakDialogView::OnThemeChanged() {
 }
 
 base::string16 CredentialLeakDialogView::GetWindowTitle() const {
-  return controller_->GetTitle();
+  // |controller_| can be nullptr when the framework calls this method after a
+  // button click.
+  return controller_ ? controller_->GetTitle() : base::string16();
 }
 
 void CredentialLeakDialogView::InitWindow() {