"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 1d5f8953769f92efbc770b3ca88331235d4d8002..9090da21044e27cab7a30fabb1a9dc049c9e167f 100644
--- a/content/browser/browsing_instance.cc
+++ b/content/browser/browsing_instance.cc
@@ -36,7 +36,6 @@ SiteInstance* BrowsingInstance::GetSiteInstanceForURL(const GURL& url) {
   if (i != site_instance_map_.end())
     return i->second;
 
-
   // No current SiteInstance for this site, so let's create one.
   SiteInstanceImpl* instance = new SiteInstanceImpl(this);
 
@@ -45,6 +44,23 @@ SiteInstance* BrowsingInstance::GetSiteInstanceForURL(const GURL& url) {
   return instance;
 }
 
+SiteInstance* BrowsingInstance::GetSiteInstanceForThirdPartySubframes(
+    const GURL& url) {
+  // If we already have a site instance for this site, always use it instead
+  // of the site instance for third party subframes.
+  if (HasSiteInstance(url))

[Charlie Reis, 2016/03/18 21:15:13]

I'm going to suggest skipping this.  Don't worry about breaking the script
connections to preexisting main frames, at least for the time being.  It would
be unusual for the subframe to depend on such a window existing.

+    return GetSiteInstanceForURL(url);
+
+  if (!site_instance_for_third_party_subframes_) {
+    SiteInstanceImpl* instance = new SiteInstanceImpl(this);
+    instance->set_is_for_third_party_subframes();
+    instance->SetSite(url);
+    site_instance_for_third_party_subframes_ = instance;
+  }
+
+  return site_instance_for_third_party_subframes_;
+}
+
 void BrowsingInstance::RegisterSiteInstance(SiteInstance* site_instance) {
   DCHECK(static_cast<SiteInstanceImpl*>(site_instance)
              ->browsing_instance_.get() ==
@@ -79,6 +95,8 @@ void BrowsingInstance::UnregisterSiteInstance(SiteInstance* site_instance) {
     // Matches, so erase it.
     site_instance_map_.erase(i);
   }
+  if (site_instance_for_third_party_subframes_ == site_instance)
+    site_instance_for_third_party_subframes_ = nullptr;
 }
 
 BrowsingInstance::~BrowsingInstance() {