Set kAlert accessibility role to the "restore pages" dialog.

This would be translated to ATK_ROLE_ALERT by the auralinux
accessibility code. Assistive technologies are expected to respond
to this role by reading the contents of the ALERT container.

Bug: 1023822
Change-Id: I763ee4047c8ba4fb09f2e77f9ddc9f6e8eaabbe9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2010846
Commit-Queue: Jacobo Aragunde Pérez <jaragunde@igalia.com>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735392}

chrome/browser/ui/views/session_crashed_bubble_view.cc

@@ -168,6 +168,10 @@ void SessionCrashedBubbleView::Show(
     RecordBubbleHistogramValue(SESSION_CRASHED_BUBBLE_ALREADY_UMA_OPTIN);
 }
 
+ax::mojom::Role SessionCrashedBubbleView::GetAccessibleWindowRole() {
+  return ax::mojom::Role::kAlert;
+}
+
 SessionCrashedBubbleView::SessionCrashedBubbleView(views::View* anchor_view,
                                                    const gfx::Rect& anchor_rect,
                                                    Browser* browser,

chrome/browser/ui/views/session_crashed_bubble_view.h

@@ -35,6 +35,10 @@ class SessionCrashedBubbleView : public SessionCrashedBubble,
   static void Show(std::unique_ptr<BrowserRemovalObserver> browser_observer,
                    bool uma_opted_in_already);
 
+ protected:
+  // views::BubbleDialogDelegateView:
+  ax::mojom::Role GetAccessibleWindowRole() override;
+
  private:
   friend class SessionCrashedBubbleViewTest;