Move existing kSitePerProcess checks to a policy-oracle object

components/guest_view/renderer/iframe_guest_view_container.cc

Index: components/guest_view/renderer/iframe_guest_view_container.cc
diff --git a/components/guest_view/renderer/iframe_guest_view_container.cc b/components/guest_view/renderer/iframe_guest_view_container.cc
index f26738304cccaa89374e12406b7ac54deb76a340..bcbdca934cca6c1fe3a40bcd5d766e342d443552 100644
--- a/components/guest_view/renderer/iframe_guest_view_container.cc
+++ b/components/guest_view/renderer/iframe_guest_view_container.cc
@@ -4,9 +4,8 @@
 
 #include "components/guest_view/renderer/iframe_guest_view_container.h"
 
-#include "base/command_line.h"
 #include "components/guest_view/common/guest_view_messages.h"
-#include "content/public/common/content_switches.h"
+#include "content/public/common/site_isolation_policy.h"
 #include "content/public/renderer/render_frame.h"
 
 namespace guest_view {
@@ -14,8 +13,7 @@ namespace guest_view {
 IframeGuestViewContainer::IframeGuestViewContainer(
     content::RenderFrame* render_frame)
     : GuestViewContainer(render_frame) {
-  CHECK(base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kSitePerProcess));
+  CHECK(content::SiteIsolationPolicy::GuestsShouldUseCrossProcessFrames());
   // There is no BrowserPluginDelegate to wait for.
   ready_ = true;
 }