Add a FOUC painting test.

Source/web/tests/sim/SimRequest.cpp

 // Copyright 2015 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 "config.h"
 #include "web/tests/sim/SimRequest.h"
 
 #include "platform/weborigin/KURL.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebURLLoaderClient.h"
@@ skipping 10 matching lines @@
     , m_isReady(false)
 {
     KURL fullUrl(ParsedURLString, url);
     WebURLResponse response(fullUrl);
     response.setMIMEType(mimeType);
     response.setHTTPStatusCode(200);
     Platform::current()->unitTestSupport()->registerMockedURL(fullUrl, response, "");
     SimNetwork::current().addRequest(*this);
 }
 
+SimRequest::~SimRequest()
+{
+    ASSERT(!m_isReady);
+}
+
 void SimRequest::didReceiveResponse(WebURLLoaderClient* client, WebURLLoader* loader, const WebURLResponse& response)
 {
     m_client = client;
     m_loader = loader;
     m_response = response;
     m_isReady = true;
 }
 
 void SimRequest::didFail(const WebURLError& error)
 {
@@ skipping 28 matching lines @@
 
 void SimRequest::reset()
 {
     m_isReady = false;
     m_client = nullptr;
     m_loader = nullptr;
     SimNetwork::current().removeRequest(*this);
 }
 
 } // namespace blink