Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

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 05429d735f9985fd2cde4d38e1f87beaeb1f4342..cba4c720af50e1bd45bc68f78676c597b8d6c080 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -77,7 +77,6 @@ class ContentSecurityPolicyResponseHeaders;
 class ContextFeatures;
 class CustomElementRegistrationContext;
 class DOMImplementation;
-class DOMNamedFlowCollection;
 class DOMSelection;
 class DOMWindow;
 class DOMWrapperWorld;
@@ -130,7 +129,6 @@ class MainThreadTaskRunner;
 class MediaQueryList;
 class MediaQueryMatcher;
 class MouseEventWithHitTestResults;
-class NamedFlowCollection;
 class NodeFilter;
 class NodeIterator;
 class Page;
@@ -321,10 +319,6 @@ public:
     PassRefPtr<Element> createElementNS(const AtomicString& namespaceURI, const AtomicString& qualifiedName, ExceptionState&);
     PassRefPtr<Element> createElement(const QualifiedName&, bool createdByParser);
 
-    PassRefPtr<DOMNamedFlowCollection> webkitGetNamedFlows();
-
-    NamedFlowCollection* namedFlows();
-
     bool regionBasedColumnsEnabled() const;
 
     /**
@@ -1322,8 +1316,6 @@ private:
 
     RefPtr<CustomElementRegistrationContext> m_registrationContext;
 
-    RefPtr<NamedFlowCollection> m_namedFlows;
-
     void elementDataCacheClearTimerFired(Timer<Document>*);
     Timer<Document> m_elementDataCacheClearTimer;