DevTools: Make all dialogs modals

Because all dialogs already fit the definition of dialog modals and all
use-cases of dialogs in the DevTools require a modal dialog.

This meets success criteria for WCAG 1.3.1 Info and Relationships
https://www.w3.org/WAI/WCAG21/quickref/#info-and-relationships

See the Dialog (Modal) design pattern for reference
https://www.w3.org/TR/wai-aria-practices-1.1/#dialog_modal

Bug: 963183
Change-Id: I9ebfeb8e54f51835351df32214512d8f5f88324b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1703029Reviewed-by: Joel Einbinder <einbinder@chromium.org>
Commit-Queue: John Emau <johnemau@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#678038}

third_party/blink/renderer/devtools/front_end/settings/SettingsScreen.js

@@ -71,7 +71,7 @@ Settings.SettingsScreen = class extends UI.VBox {
         /** @type {!Settings.SettingsScreen} */ (self.runtime.sharedInstance(Settings.SettingsScreen));
     if (settingsScreen.isShowing())
       return;
-    const dialog = new UI.Dialog(/* modal=*/ true);
+    const dialog = new UI.Dialog();
     dialog.addCloseButton();
     settingsScreen.show(dialog.contentElement);
     dialog.show();

third_party/blink/renderer/devtools/front_end/ui/Dialog.js

@@ -29,10 +29,8 @@
  */
 
 UI.Dialog = class extends UI.GlassPane {
-  /**
-   * @param {boolean=} modal
-   */
-  constructor(modal) {
+
+  constructor() {
     super();
     this.registerRequiredCSS('ui/dialog.css');
     this.contentElement.tabIndex = 0;
@@ -44,7 +42,7 @@ UI.Dialog = class extends UI.GlassPane {
       this.hide();
       event.consume(true);
     });
-    UI.ARIAUtils.markAsDialog(this.contentElement, modal);
+    UI.ARIAUtils.markAsDialog(this.contentElement, true);
     /** @type {!Map<!HTMLElement, number>} */
     this._tabIndexMap = new Map();
     /** @type {?UI.WidgetFocusRestorer} */