Allow embedders to provide a custom view for popup (select box) widgets,

content/browser/web_contents/web_contents_view_mac.mm

Index: content/browser/web_contents/web_contents_view_mac.mm
===================================================================
--- content/browser/web_contents/web_contents_view_mac.mm	(revision 176042)
+++ content/browser/web_contents/web_contents_view_mac.mm	(working copy)
@@ -142,6 +142,11 @@
   return view;
 }
 
+RenderWidgetHostView* WebContentsViewMac::CreateViewForPopupWidget(
+    RenderWidgetHost* render_widget_host) {
+  return RenderWidgetHostViewPort::CreateViewForWidget(render_widget_host);
+}
+
 gfx::NativeView WebContentsViewMac::GetNativeView() const {
   return cocoa_view_.get();
 }