Don't split off NTP subframes with TDI.

content/public/browser/content_browser_client.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_PUBLIC_BROWSER_CONTENT_BROWSER_CLIENT_H_
 #define CONTENT_PUBLIC_BROWSER_CONTENT_BROWSER_CLIENT_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 224 matching lines @@
   // This also applies in cases where the new URL will open in another process.
   virtual bool ShouldAllowOpenURL(SiteInstance* site_instance, const GURL& url);
 
   // Allows the embedder to override parameters when navigating. Called for both
   // opening new URLs and when transferring URLs across processes.
   virtual void OverrideNavigationParams(SiteInstance* site_instance,
                                         ui::PageTransition* transition,
                                         bool* is_renderer_initiated,
                                         content::Referrer* referrer) {}
 
+  // Allows the embedder to override top document isolation for specific frames.
+  // |url| is the URL being loaded in the subframe, and |site_instance| is the
+  // SiteInstance of the parent frame. Called only for subframes and only when
+  // top document isolation mode is enabled.
+  virtual bool ShouldFrameShareParentSiteInstanceDespiteTopDocumentIsolation(
+      const GURL& url,
+      SiteInstance* site_instance);

[ncarter (slow), 2016/11/15 21:42:35]

WDYT about renaming |site_instance| -> |parent_site_instance| ?

[Avi (use Gerrit), 2016/11/16 20:12:11]

Done.

+
   // Returns whether a new view for a given |site_url| can be launched in a
   // given |process_host|.
   virtual bool IsSuitableHost(RenderProcessHost* process_host,
                               const GURL& site_url);
 
   // Returns whether a new view for a new site instance can be added to a
   // given |process_host|.
   virtual bool MayReuseHost(RenderProcessHost* process_host);
 
   // Returns whether a new process should be created or an existing one should
@@ skipping 516 matching lines @@
 #endif
 
   // Returns an instance of MemoryCoordinatorDelegate.
   virtual std::unique_ptr<MemoryCoordinatorDelegate>
   GetMemoryCoordinatorDelegate();
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_CONTENT_BROWSER_CLIENT_H_