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

content/browser/browser_plugin/browser_plugin_popup_menu_helper_mac.mm

Index: content/browser/browser_plugin/browser_plugin_popup_menu_helper_mac.mm
diff --git a/content/browser/browser_plugin/browser_plugin_popup_menu_helper_mac.mm b/content/browser/browser_plugin/browser_plugin_popup_menu_helper_mac.mm
index 1874747f97f3033c8fa730195eaaa78672287604..1784e0e900f3771c5559bd18f62c1d6a79a2e8f7 100644
--- a/content/browser/browser_plugin/browser_plugin_popup_menu_helper_mac.mm
+++ b/content/browser/browser_plugin/browser_plugin_popup_menu_helper_mac.mm
@@ -13,11 +13,16 @@ namespace content {
 BrowserPluginPopupMenuHelper::BrowserPluginPopupMenuHelper(
     RenderFrameHostImpl* embedder_rfh,
     RenderFrameHost* guest_rfh)
-    : PopupMenuHelper(guest_rfh), embedder_rfh_(embedder_rfh) {}
+    : PopupMenuHelper(this, guest_rfh), embedder_rfh_(embedder_rfh) {}
 
 RenderWidgetHostViewMac*
     BrowserPluginPopupMenuHelper::GetRenderWidgetHostView() const {
   return static_cast<RenderWidgetHostViewMac*>(embedder_rfh_->GetView());
 }
 
+void BrowserPluginPopupMenuHelper::OnMenuClosed() {
+  // BrowserPluginGuest doesn't support cancellation of popup menus, so the
+  // MenuHelper is its own delegate and OnMenuClosed() is ignored.
+}
+
 }  // namespace content