"Top Document Isolation" mode

content/common/site_isolation_policy.cc

Index: content/common/site_isolation_policy.cc
diff --git a/content/common/site_isolation_policy.cc b/content/common/site_isolation_policy.cc
index 694c9db3336be49465f81223f9f2f49e70575a07..b25741b3b39b2f0b5dada6f17313406071c81b09 100644
--- a/content/common/site_isolation_policy.cc
+++ b/content/common/site_isolation_policy.cc
@@ -15,8 +15,8 @@ namespace content {
 
 // static
 bool SiteIsolationPolicy::AreCrossProcessFramesPossible() {
-  return base::CommandLine::ForCurrentProcess()->HasSwitch(
-             switches::kSitePerProcess) ||
+  return UseDedicatedProcessesForAllSites() ||
+         IsTopDocumentIsolationEnabled() ||
          GetContentClient()->IsSupplementarySiteIsolationModeEnabled() ||
          BrowserPluginGuestMode::UseCrossProcessFramesForGuests();
 }
@@ -28,6 +28,16 @@ bool SiteIsolationPolicy::UseDedicatedProcessesForAllSites() {
 }
 
 // static
+bool SiteIsolationPolicy::IsTopDocumentIsolationEnabled() {
+  // --site-per-process trumps --top-document-isolation.
+  if (UseDedicatedProcessesForAllSites())
+    return false;
+
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kTopDocumentIsolation);
+}
+
+// static
 bool SiteIsolationPolicy::UseSubframeNavigationEntries() {
   // Enable the new navigation history behavior if any manner of site isolation
   // is active.