Do not block painting for in-body CSS

third_party/WebKit/Source/core/dom/StyleEngineContext.h

+// Copyright (c) 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 StyleEngineContext_h
+#define StyleEngineContext_h
+
+#include "core/dom/Document.h"
+
+namespace blink {
+
+class StyleEngineContext {
+public:
+    StyleEngineContext() : m_addedPendingSheetBeforeBody(false) {}
+    ~StyleEngineContext() {}
+    bool addedPendingSheetBeforeBody() const { return m_addedPendingSheetBeforeBody; }
+    void addingPendingSheet(const Document& document) { m_addedPendingSheetBeforeBody = m_addedPendingSheetBeforeBody || !document.body(); }
+private:
+    bool m_addedPendingSheetBeforeBody : 1;
+};
+
+} // namespace blink
+
+#endif