Move existing kSitePerProcess checks to a policy-oracle object

content/browser/frame_host/frame_tree_node.cc

Index: content/browser/frame_host/frame_tree_node.cc
diff --git a/content/browser/frame_host/frame_tree_node.cc b/content/browser/frame_host/frame_tree_node.cc
index 67d9b8336e4c1dfd32c24d94557256b504b9c365..1f1b9dca05c10a91cb67cbd8ab49ccc31c831173 100644
--- a/content/browser/frame_host/frame_tree_node.cc
+++ b/content/browser/frame_host/frame_tree_node.cc
@@ -15,6 +15,7 @@
 #include "content/browser/frame_host/render_frame_host_impl.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/common/frame_messages.h"
+#include "content/common/site_isolation_policy.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_switches.h"
 
@@ -140,8 +141,8 @@ void FrameTreeNode::AddChild(scoped_ptr<FrameTreeNode> child,
   // about the new frame.  Create a proxy for the child frame in all
   // SiteInstances that have a proxy for the frame's parent, since all frames
   // in a frame tree should have the same set of proxies.
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kSitePerProcess))
+  // TODO(alexmos, nick): We ought to do this for non-oopif too, for openers.
+  if (SiteIsolationPolicy::AreCrossProcessFramesPossible())
     render_manager_.CreateProxiesForChildFrame(child.get());
 
   children_.push_back(child.release());