Move StyleSheetContents cache to StyleEngine.

Source/core/dom/StyleElement.cpp

Index: Source/core/dom/StyleElement.cpp
diff --git a/Source/core/dom/StyleElement.cpp b/Source/core/dom/StyleElement.cpp
index 5d377b816b5e2a3e33d761d8afe4789a1ed7cb8a..c16c57fb3399988fe8c957af152d4fb0c8ed173b 100644
--- a/Source/core/dom/StyleElement.cpp
+++ b/Source/core/dom/StyleElement.cpp
@@ -148,7 +148,7 @@ void StyleElement::createSheet(Element* e, const String& text)
         if (screenEval.eval(mediaQueries.get()) || printEval.eval(mediaQueries.get())) {
             m_loading = true;
             TextPosition startPosition = m_startPosition == TextPosition::belowRangePosition() ? TextPosition::minimumPosition() : m_startPosition;
-            m_sheet = StyleEngine::createSheet(e, text, startPosition, m_createdByParser);
+            m_sheet = document.styleEngine()->createSheet(e, text, startPosition, m_createdByParser);
             m_sheet->setMediaQueries(mediaQueries.release());
             m_loading = false;
         }