Have StyleResolver / StyleResolverState deal with Document references, not pointers

Source/core/css/resolver/StyleResolver.h

Index: Source/core/css/resolver/StyleResolver.h
diff --git a/Source/core/css/resolver/StyleResolver.h b/Source/core/css/resolver/StyleResolver.h
index 2ce8755d4f2636fb10e19a53b64e1ff555d2b222..def50bcfc3ed7b1b4b84bf380f3f6a91ca7162fb 100644
--- a/Source/core/css/resolver/StyleResolver.h
+++ b/Source/core/css/resolver/StyleResolver.h
@@ -172,7 +172,7 @@ struct CSSPropertyValue {
 class StyleResolver {
     WTF_MAKE_NONCOPYABLE(StyleResolver); WTF_MAKE_FAST_ALLOCATED;
 public:
-    StyleResolver(Document*, bool matchAuthorAndUserStyles);
+    StyleResolver(Document&, bool matchAuthorAndUserStyles);
     ~StyleResolver();
 
     // FIXME: StyleResolver should not be keeping tree-walk state.
@@ -202,11 +202,11 @@ public:
     PassRefPtr<RenderStyle> defaultStyleForElement();
     PassRefPtr<RenderStyle> styleForText(Text*);
 
-    static PassRefPtr<RenderStyle> styleForDocument(const Document*, CSSFontSelector* = 0);
+    static PassRefPtr<RenderStyle> styleForDocument(const Document&, CSSFontSelector* = 0);
 
     // FIXME: This only has 5 callers and should be removed. Callers should be explicit about
     // their dependency on Document* instead of grabbing one through StyleResolver.
-    Document* document() { return m_document; }
+    Document& document() { return m_document; }
 
     // FIXME: It could be better to call m_ruleSets.appendAuthorStyleSheets() directly after we factor StyleRsolver further.
     // https://bugs.webkit.org/show_bug.cgi?id=108890
@@ -224,7 +224,7 @@ public:
 
     ScopedStyleResolver* ensureScopedStyleResolver(const ContainerNode* scope)
     {
-        return m_styleTree.ensureScopedStyleResolver(scope ? scope : document());
+        return m_styleTree.ensureScopedStyleResolver(scope ? scope : &document());
     }
 
     // FIXME: Used by SharingStyleFinder, but should be removed.
@@ -310,7 +310,7 @@ private:
     void matchPageRules(MatchResult&, RuleSet*, bool isLeftPage, bool isFirstPage, const String& pageName);
     void matchPageRulesForList(Vector<StyleRulePage*>& matchedRules, const Vector<StyleRulePage*>&, bool isLeftPage, bool isFirstPage, const String& pageName);
     void collectViewportRules();
-    Settings* documentSettings() { return m_document->settings(); }
+    Settings* documentSettings() { return m_document.settings(); }
 
     bool isLeftPage(int pageIndex) const;
     bool isRightPage(int pageIndex) const { return !isLeftPage(pageIndex); }
@@ -332,7 +332,7 @@ private:
     OwnPtr<MediaQueryEvaluator> m_medium;
     RefPtr<RenderStyle> m_rootDefaultStyle;
 
-    Document* m_document;
+    Document& m_document;
     SelectorFilter m_selectorFilter;
 
     bool m_matchAuthorAndUserStyles;