Handle WebContentsViewMac being destroyed while a <select> menu is showing.

content/browser/web_contents/web_contents_view_mac.mm

Index: content/browser/web_contents/web_contents_view_mac.mm
diff --git a/content/browser/web_contents/web_contents_view_mac.mm b/content/browser/web_contents/web_contents_view_mac.mm
index 2b457494ab70022635a2033e92c34dad367d2f67..ebd0ce35c1c1aeae9462cafc348722bb01224b5e 100644
--- a/content/browser/web_contents/web_contents_view_mac.mm
+++ b/content/browser/web_contents/web_contents_view_mac.mm
@@ -307,11 +307,11 @@ void WebContentsViewMac::ShowPopupMenu(
     const std::vector<MenuItem>& items,
     bool right_aligned,
     bool allow_multiple_selection) {
-  popup_menu_helper_.reset(new PopupMenuHelper(render_frame_host));
+  popup_menu_helper_.reset(new PopupMenuHelper(this, render_frame_host));
   popup_menu_helper_->ShowPopupMenu(bounds, item_height, item_font_size,
                                     selected_item, items, right_aligned,
                                     allow_multiple_selection);
-  popup_menu_helper_.reset();
+  // Note: |this| may be deleted here.
 }
 
 void WebContentsViewMac::HidePopupMenu() {
@@ -319,6 +319,10 @@ void WebContentsViewMac::HidePopupMenu() {
     popup_menu_helper_->Hide();
 }
 
+void WebContentsViewMac::OnMenuClosed() {
+  popup_menu_helper_.reset();
+}
+
 gfx::Rect WebContentsViewMac::GetViewBounds() const {
   // This method is not currently used on mac.
   NOTIMPLEMENTED();