Use FrameIsAd to decide whether to isolate a frame in TopDocumentIsolation mode.

content/public/browser/content_browser_client.cc

Index: content/public/browser/content_browser_client.cc
diff --git a/content/public/browser/content_browser_client.cc b/content/public/browser/content_browser_client.cc
index 5193ae1ea4c54ed70d145c48b18584c675fd2358..6c21a2c55d75d2942bc79358322a63a664d9ccb2 100644
--- a/content/public/browser/content_browser_client.cc
+++ b/content/public/browser/content_browser_client.cc
@@ -92,11 +92,13 @@ bool ContentBrowserClient::ShouldAllowOpenURL(SiteInstance* site_instance,
   return true;
 }
 
-bool ContentBrowserClient::
-    ShouldFrameShareParentSiteInstanceDespiteTopDocumentIsolation(
-        const GURL& url,
-        SiteInstance* parent_site_instance) {
-  return false;
+bool ContentBrowserClient::ShouldIsolateFrameForTopDocumentIsolation(
+    NavigationHandle* navigation_handle,
+    SiteInstance* main_frame_site_instance) {
+  // In absence of customizations above //content layer, TDI mode should isolate
+  // all cross-site frames.  Additionally, isolating all cross-site frames makes
+  // it easier to test TopDocumentIsolation in content_browsertests.
+  return true;
 }
 
 bool ContentBrowserClient::IsSuitableHost(RenderProcessHost* process_host,