Revert of Remove about:srcdoc url conversion.

content/browser/frame_host/render_frame_host_manager.cc

 // Copyright 2013 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.
 
 #include "content/browser/frame_host/render_frame_host_manager.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 1388 matching lines @@
   // chrome://crash, however.
   // TODO(creis): Refactor this method so this duplicated code isn't needed.
   // See http://crbug.com/123007.
   if (current_entry &&
       current_entry->IsViewSourceMode() != dest_is_view_source_mode &&
       !IsRendererDebugURL(dest_url)) {
     return SiteInstanceDescriptor(browser_context, dest_url,
                                   SiteInstanceRelation::UNRELATED);
   }
 
-  // Use the source SiteInstance in case of data URLs, about:srcdoc pages and
-  // about:blank pages because the content is then controlled and/or scriptable
-  // by the source SiteInstance.
+  // Use the source SiteInstance in case of data URLs or about:blank pages,
+  // because the content is then controlled and/or scriptable by the source
+  // SiteInstance.
   GURL about_blank(url::kAboutBlankURL);
-  GURL about_srcdoc(content::kAboutSrcDocURL);
-  if (source_instance && (dest_url == about_srcdoc || dest_url == about_blank ||
-                          dest_url.scheme() == url::kDataScheme)) {
+  if (source_instance &&
+      (dest_url == about_blank || dest_url.scheme() == url::kDataScheme)) {
     return SiteInstanceDescriptor(source_instance);
   }
 
   // Use the current SiteInstance for same site navigations.
   if (IsCurrentlySameSite(render_frame_host_.get(), dest_url))
     return SiteInstanceDescriptor(render_frame_host_->GetSiteInstance());
 
   if (SiteIsolationPolicy::IsTopDocumentIsolationEnabled()) {
     // TODO(nick): Looking at the main frame and openers is required for TDI
     // mode, but should be safe to enable unconditionally.
@@ skipping 1310 matching lines @@
                                              resolved_url)) {
     DCHECK(!dest_instance ||
            dest_instance == render_frame_host_->GetSiteInstance());
     return false;
   }
 
   return true;
 }
 
 }  // namespace content