"Top Document Isolation" mode

content/browser/browsing_instance.cc

Index: content/browser/browsing_instance.cc
diff --git a/content/browser/browsing_instance.cc b/content/browser/browsing_instance.cc
index b68a87ccbf69d65c171a5390f3833c7b98cf1ca2..5dd0ca4191fe832c5d4eea078c9cab946a8d397b 100644
--- a/content/browser/browsing_instance.cc
+++ b/content/browser/browsing_instance.cc
@@ -7,6 +7,7 @@
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "content/browser/site_instance_impl.h"
+#include "content/common/site_isolation_policy.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/common/content_switches.h"
@@ -44,9 +45,32 @@ scoped_refptr<SiteInstanceImpl> BrowsingInstance::GetSiteInstanceForURL(
   return instance;
 }
 
+scoped_refptr<SiteInstanceImpl>
+BrowsingInstance::GetDefaultSubframeSiteInstance() {
+  // This should only be used for --top-document-isolation mode.
+  CHECK(SiteIsolationPolicy::IsTopDocumentIsolationEnabled());
+  if (!default_subframe_site_instance_) {
+    SiteInstanceImpl* instance = new SiteInstanceImpl(this);
+    instance->set_is_default_subframe_site_instance();
+
+    // TODO(nick): This is a hack for now.
+    instance->SetSite(GURL("http://web-subframes.invalid"));
+
+    default_subframe_site_instance_ = instance;
+  }
+
+  return make_scoped_refptr(default_subframe_site_instance_);
+}
+
 void BrowsingInstance::RegisterSiteInstance(SiteInstanceImpl* site_instance) {
   DCHECK(site_instance->browsing_instance_.get() == this);
   DCHECK(site_instance->HasSite());
+
+  // Don't register the default subframe SiteInstance, to prevent it from being
+  // returned by GetSiteInstanceForURL.
+  if (default_subframe_site_instance_ == site_instance)
+    return;
+
   std::string site = site_instance->GetSiteURL().possibly_invalid_spec();
 
   // Only register if we don't have a SiteInstance for this site already.
@@ -74,6 +98,8 @@ void BrowsingInstance::UnregisterSiteInstance(SiteInstanceImpl* site_instance) {
     // Matches, so erase it.
     site_instance_map_.erase(i);
   }
+  if (default_subframe_site_instance_ == site_instance)
+    default_subframe_site_instance_ = nullptr;
 }
 
 BrowsingInstance::~BrowsingInstance() {