Add a content_shell flag to turn on partial site isolation.

content/shell/common/shell_content_client.cc

 // 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.
 
 #include "content/shell/common/shell_content_client.h"
 
 #include "base/command_line.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/utf_string_conversions.h"
 #include "blink/public/resources/grit/blink_image_resources.h"
@@ skipping 73 matching lines @@
 
 base::RefCountedStaticMemory* ShellContentClient::GetDataResourceBytes(
     int resource_id) const {
   return ResourceBundle::GetSharedInstance().LoadDataResourceBytes(resource_id);
 }
 
 gfx::Image& ShellContentClient::GetNativeImageNamed(int resource_id) const {
   return ResourceBundle::GetSharedInstance().GetNativeImageNamed(resource_id);
 }
 
+bool ShellContentClient::IsSupplementarySiteIsolationModeEnabled() {
+  return base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kIsolateSitesForTesting);
+}
+
 }  // namespace content