Add a FOUC painting test.

Source/web/tests/sim/SimDisplayItemList.h

+// 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.
+
+#ifndef SimDisplayItemList_h
+#define SimDisplayItemList_h
+
+#include "public/platform/WebDisplayItemList.h"
+#include "web/tests/sim/SimCanvas.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+class SimDisplayItemList final : public WebDisplayItemList {
+public:
+    SimDisplayItemList();
+
+    void appendDrawingItem(const SkPicture*) override;
+
+    int drawCount() const { return m_commands.size(); }
+
+    bool containsText() const { return m_containsText; }
+    bool contains(SimCanvas::CommandType, const String& colorString = String()) const;
+
+private:
+    bool m_containsText;
+    Vector<SimCanvas::Command> m_commands;
+};
+
+} // namespace blink
+
+#endif