Inside of content, prefer SiteInstanceImpl to SiteInstance.

content/browser/browser_plugin/browser_plugin_guest.cc

Index: content/browser/browser_plugin/browser_plugin_guest.cc
diff --git a/content/browser/browser_plugin/browser_plugin_guest.cc b/content/browser/browser_plugin/browser_plugin_guest.cc
index fd0c173ed0b97c250546934846d0ac482e19d88b..7c0fe743ee353810ecf4c9c3e1c0181ff119dbe6 100644
--- a/content/browser/browser_plugin/browser_plugin_guest.cc
+++ b/content/browser/browser_plugin/browser_plugin_guest.cc
@@ -130,7 +130,8 @@ int BrowserPluginGuest::GetGuestProxyRoutingID() {
   // owners in different processes. We probably need to clear the
   // |guest_proxy_routing_id_| and perform any necessary cleanup on Detach
   // to enable this.
-  SiteInstance* owner_site_instance = owner_web_contents_->GetSiteInstance();
+  SiteInstanceImpl* owner_site_instance =
+      owner_web_contents_->GetSiteInstance();
   int proxy_routing_id =
       GetWebContents()->GetFrameTree()->root()->render_manager()->
           CreateRenderFrameProxy(owner_site_instance);