Refactoring: Simplify DocumentWriter by reorganizing its lifetime.

Source/core/loader/DocumentLoader.h

Index: Source/core/loader/DocumentLoader.h
diff --git a/Source/core/loader/DocumentLoader.h b/Source/core/loader/DocumentLoader.h
index c9a8a9ae36a8bf8429e56289d5471a8610ce40e8..18f3151c1cc208596eb645d25496ecb12afd416c 100644
--- a/Source/core/loader/DocumentLoader.h
+++ b/Source/core/loader/DocumentLoader.h
@@ -85,6 +85,8 @@ namespace WebCore {
 
         void replaceDocument(const String& source, Document*);
         DocumentWriter* beginWriting(const String& mimeType, const String& encoding, const KURL& = KURL());
+        void endWriting(DocumentWriter*);
+
         String mimeType() const;
 
         const ResourceRequest& originalRequest() const;
@@ -162,6 +164,10 @@ namespace WebCore {
         bool m_deferMainResourceDataLoad;
 
     private:
+        static PassRefPtr<DocumentWriter> createWriterFor(Frame*, const Document* ownerDocument, const KURL&, const String& mimeType, const String& encoding, bool userChosen, bool dispatch);
+
+        void ensureWriter();
+        void ensureWriter(const String& mimeType, const KURL& overridingURL = KURL());
 
         // The URL of the document resulting from this DocumentLoader.
         KURL documentURL() const;
@@ -177,7 +183,7 @@ namespace WebCore {
         void clearMainResourceHandle();
         PassRefPtr<SharedBuffer> mainResourceData() const;
 
-        bool maybeCreateArchive();
+        void createArchive();
         void clearArchiveResources();
 
         void prepareSubframeArchiveLoadIfNeeded();
@@ -212,7 +218,7 @@ namespace WebCore {
         ResourceLoaderSet m_resourceLoaders;
         ResourceLoaderSet m_multipartResourceLoaders;
         
-        mutable DocumentWriter m_writer;
+        RefPtr<DocumentWriter> m_writer;
 
         // A reference to actual request used to create the data source.
         // This should only be used by the resourceLoadDelegate's
@@ -237,7 +243,6 @@ namespace WebCore {
 
         bool m_committed;
         bool m_isStopping;
-        bool m_gotFirstByte;
         bool m_isClientRedirect;
 
         // FIXME: Document::m_processingLoadEvent and DocumentLoader::m_wasOnloadHandled are roughly the same