DevTools: create test infrastructure so devtools drives the test

content/shell/browser/layout_test/blink_test_controller.h

Index: content/shell/browser/layout_test/blink_test_controller.h
diff --git a/content/shell/browser/layout_test/blink_test_controller.h b/content/shell/browser/layout_test/blink_test_controller.h
index a96d88844c84626b5f93bbb689198eccb86087b9..d68ef8b6766d1c382bab81cf76195b1227206650 100644
--- a/content/shell/browser/layout_test/blink_test_controller.h
+++ b/content/shell/browser/layout_test/blink_test_controller.h
@@ -194,6 +194,8 @@ class BlinkTestController : public WebContentsObserver,
 
   static BlinkTestController* instance_;
 
+  Shell* SecondaryWindow();
+  void LoadDevToolsJSTest();
   void DiscardMainWindow();
 
   // Message handlers.
@@ -232,6 +234,7 @@ class BlinkTestController : public WebContentsObserver,
   base::FilePath temp_path_;
 
   Shell* main_window_;
+  Shell* secondary_window_;
   Shell* devtools_window_;
 
   std::unique_ptr<LayoutTestDevToolsBindings> devtools_bindings_;