One and only one top-loading-frame across all renderers.

components/test_runner/layout_test_runtime_flags.h

 // Copyright 2016 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 COMPONENTS_TEST_RUNNER_LAYOUT_TEST_RUNTIME_FLAGS_H_
 #define COMPONENTS_TEST_RUNNER_LAYOUT_TEST_RUNTIME_FLAGS_H_
 
 #include <string>
 
 #include "base/logging.h"
@@ skipping 140 matching lines @@
   // If true, output a message when the page title is changed.
   DEFINE_BOOL_LAYOUT_TEST_RUNTIME_FLAG(dump_title_changes)
 
   // If true, the test_shell will print out the icon change notifications.
   DEFINE_BOOL_LAYOUT_TEST_RUNTIME_FLAG(dump_icon_changes)
 
   // Desired return value of WebFrameClient::runModalBeforeUnloadDialog.
   DEFINE_BOOL_LAYOUT_TEST_RUNTIME_FLAG(
       stay_on_page_after_handling_before_unload)
 
+  // Flag to try to prevent different renderer processes tracking
+  // different top loading frames.
+  DEFINE_BOOL_LAYOUT_TEST_RUNTIME_FLAG(have_top_loading_frame)
+
 #undef DEFINE_BOOL_LAYOUT_TEST_RUNTIME_FLAG
 #undef DEFINE_STRING_LAYOUT_TEST_RUNTIME_FLAG
 
   // Reports whether recursing over child frames is necessary.
   bool dump_child_frames() const {
     if (dump_as_text())
       return dump_child_frames_as_text();
     else if (dump_as_markup())
       return dump_child_frames_as_markup();
     else
       return dump_child_frame_scroll_positions();
   }
 
  private:
   TrackedDictionary dict_;
 
   DISALLOW_COPY_AND_ASSIGN(LayoutTestRuntimeFlags);
 };
 
 }  // namespace test_runner
 
 #endif  // COMPONENTS_TEST_RUNNER_LAYOUT_TEST_RUNTIME_FLAGS_H_