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

content/shell/browser/shell_content_browser_client.cc

Index: content/shell/browser/shell_content_browser_client.cc
diff --git a/content/shell/browser/shell_content_browser_client.cc b/content/shell/browser/shell_content_browser_client.cc
index 62fb2b6201b4e70dbaebdba10720dc637def9379..18c1cdebfdcff90ce790662abe5a3d2ffdaf91bd 100644
--- a/content/shell/browser/shell_content_browser_client.cc
+++ b/content/shell/browser/shell_content_browser_client.cc
@@ -6,6 +6,7 @@
 
 #include <stddef.h>
 #include <utility>
+#include <vector>
 
 #include "base/base_switches.h"
 #include "base/command_line.h"
@@ -347,6 +348,16 @@ net::NetLog* ShellContentBrowserClient::GetNetLog() {
   return shell_browser_main_parts_->net_log();
 }
 
+bool ShellContentBrowserClient::ShouldIsolateFrameFromMainContent(
+    content::RenderFrameHost* frame,
+    const GURL& dest_url,
+    content::SiteInstance* main_frame_site_instance) {
+  // To make it easier to test TopDocumentIsolation in content_browsertests,
+  // put *all* cross-site subframes into the TDI process (when TDI mode is
+  // enabled).
+  return true;
+}
+
 bool ShellContentBrowserClient::ShouldSwapProcessesForRedirect(
     BrowserContext* browser_context,
     const GURL& current_url,