Use process-per-app-instance for hosted apps without background permission.

content/browser/site_instance.cc

Index: content/browser/site_instance.cc
diff --git a/content/browser/site_instance.cc b/content/browser/site_instance.cc
index d69690e2ab2bc5b20c1a1ba7593262837472622a..442c80796b15da971ff3b006f78af1f65894cad8 100644
--- a/content/browser/site_instance.cc
+++ b/content/browser/site_instance.cc
@@ -42,6 +42,11 @@ SiteInstance::SiteInstance(BrowsingInstance* browsing_instance)
 }
 
 SiteInstance::~SiteInstance() {
+  NotificationService::current()->Notify(
+      content::NOTIFICATION_SITE_INSTANCE_DELETED,
+      Source<SiteInstance>(this),
+      NotificationService::NoDetails());
+
   // Now that no one is referencing us, we can safely remove ourselves from
   // the BrowsingInstance.  Any future visits to a page from this site
   // (within the same BrowsingInstance) can safely create a new SiteInstance.