RenderWidget popup should be a NSWindow so it can go outside the main window.

content/browser/renderer_host/render_widget_host_view_mac.h

Index: content/browser/renderer_host/render_widget_host_view_mac.h
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.h b/content/browser/renderer_host/render_widget_host_view_mac.h
index 9255c07b646ebad5456778fc0bcb0d73f675b7e5..7b307a5499d504f594e121109d679532852197ad 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.h
+++ b/content/browser/renderer_host/render_widget_host_view_mac.h
@@ -477,6 +477,9 @@ class RenderWidgetHostViewMac : public RenderWidgetHostViewBase {
   // selected text on the renderer.
   std::string selected_text_;
 
+  // The window used for popup widgets.
+  scoped_nsobject<NSWindow> popup_window_;
+
   // The fullscreen window used for pepper flash.
   scoped_nsobject<NSWindow> pepper_fullscreen_window_;
   scoped_nsobject<FullscreenWindowManager> fullscreen_window_manager_;