Allow WebUI Tests to use preLoad in HtmlDialogUI.

chrome/test/base/js_injection_ready_observer.h

+// Copyright (c) 2011 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 CHROME_TEST_BASE_JS_INJECTION_READY_OBSERVER_H_
+#define CHROME_TEST_BASE_JS_INJECTION_READY_OBSERVER_H_
+#pragma once
+
+class RenderViewHost;
+
+// Interface to notify when JavaScript injection is possible.
+class JsInjectionReadyObserver {
+ public:
+  // Called to indicate page entry committed and ready for JavaScript
+  // injection. |render_view_host| may be used to route injection messages to
+  // the appropriate RenderView.
+  virtual void OnJsInjectionReady(RenderViewHost* render_view_host) = 0;
+
+ protected:
+  virtual ~JsInjectionReadyObserver() {}
+};
+
+#endif  // CHROME_TEST_BASE_JS_INJECTION_READY_OBSERVER_H_