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 409a2a84932d6b0330cadc30c3eaa7e9121a972a..4478ac2df445cd54caeea11d3082f630302443db 100644
--- a/content/browser/frame_host/frame_tree_node.cc
+++ b/content/browser/frame_host/frame_tree_node.cc
@@ -16,6 +16,7 @@
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_switches.h"
+#include "content/public/common/site_isolation_policy.h"
 
 namespace content {
 
@@ -138,8 +139,8 @@ 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());