Return reference from styleEngine() accessor.

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index ac9693662f0c6738a20b0ed57f0f218674fc0855..ff8de6407bb41b0f7bc41229f1799f4e54f9e066 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -421,7 +421,7 @@ public:
     // This is a DOM function.
     StyleSheetList* styleSheets();
 
-    StyleEngine* styleEngine() { return m_styleEngine.get(); }
+    StyleEngine& styleEngine() { ASSERT(m_styleEngine.get()); return *m_styleEngine.get(); }
 
     bool gotoAnchorNeededAfterStylesheetsLoad() { return m_gotoAnchorNeededAfterStylesheetsLoad; }
     void setGotoAnchorNeededAfterStylesheetsLoad(bool b) { m_gotoAnchorNeededAfterStylesheetsLoad = b; }
@@ -990,7 +990,6 @@ public:
 
     void didLoadAllScriptBlockingResources();
     void didRemoveAllPendingStylesheet();
-    void clearStyleResolver();
 
     bool inStyleRecalc() const { return m_lifecycle.state() == DocumentLifecycle::InStyleRecalc; }