Remove WebDialogView::ShouldShowCloseButton() override for login screen

login_screen_extension_ui::WebDialogView::ShouldShowCloseButton() calls
WebDialogDelegate::CanCloseDialog(), which is being removed in cl
2278793.

This CL removes the ShouldShowCloseButton() override and makes necessary
changes to the login_screen_extension_ui::DialogDelegate so that the
default ShouldShowCloseButton() will work as expected.

Bug: 970196
Change-Id: I6cfeb25f3fb264cbe325d83acaafe9a69e7e366d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2319491Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Jason Lin <lxj@google.com>
Cr-Commit-Position: refs/heads/master@{#792507}

chrome/browser/chromeos/login/ui/login_screen_extension_ui/dialog_delegate.cc

@@ -89,6 +89,10 @@ bool DialogDelegate::ShouldCenterDialogTitleText() const {
   return true;
 }
 
+bool DialogDelegate::ShouldShowCloseButton() const {
+  return can_close_;
+}
+
 }  // namespace login_screen_extension_ui
 
 }  // namespace chromeos

chrome/browser/chromeos/login/ui/login_screen_extension_ui/dialog_delegate.h

@@ -59,6 +59,7 @@ class DialogDelegate : public ui::WebDialogDelegate {
   bool ShouldCloseDialogOnEscape() const override;
   bool ShouldShowDialogTitle() const override;
   bool ShouldCenterDialogTitleText() const override;
+  bool ShouldShowCloseButton() const override;
 
  private:
   const std::string extension_name_;

chrome/browser/chromeos/login/ui/login_screen_extension_ui/web_dialog_view.cc

@@ -33,10 +33,6 @@ WebDialogView::~WebDialogView() {
   }
 }
 
-bool WebDialogView::ShouldShowCloseButton() const {
-  return !delegate_ || delegate_->CanCloseDialog();
-}
-
 bool WebDialogView::TakeFocus(content::WebContents* source, bool reverse) {
   ash::LoginScreen::Get()->FocusLoginShelf(reverse);
   return true;

chrome/browser/chromeos/login/ui/login_screen_extension_ui/web_dialog_view.h

@@ -37,7 +37,6 @@ class WebDialogView : public views::WebDialogView,
   ~WebDialogView() override;
 
   // views::WebDialogView
-  bool ShouldShowCloseButton() const override;
   bool TakeFocus(content::WebContents* source, bool reverse) override;
 
   // ash::SystemTrayFocusObserver