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 cd6f05c0626e8bc48485bc5f26cff7b0a465617f..bb7d7ca87d45ef1e5a4715e7a44cdc29e77c514c 100644
--- a/Source/core/loader/DocumentLoader.h
+++ b/Source/core/loader/DocumentLoader.h
@@ -86,6 +86,8 @@ 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;
@@ -167,6 +169,10 @@ namespace WebCore {
         bool m_deferMainResourceDataLoad;
 
     private:
+        static PassOwnPtr<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);
 
         // The URL of the document resulting from this DocumentLoader.
         KURL documentURL() const;
@@ -182,7 +188,7 @@ namespace WebCore {
         void clearMainResourceHandle();
         PassRefPtr<SharedBuffer> mainResourceData() const;
 
-        bool maybeCreateArchive();
+        void createArchive();
         void clearArchiveResources();
 
         void prepareSubframeArchiveLoadIfNeeded();
@@ -217,7 +223,7 @@ namespace WebCore {
         ResourceLoaderSet m_resourceLoaders;
         ResourceLoaderSet m_multipartResourceLoaders;
         
-        mutable DocumentWriter m_writer;
+        OwnPtr<DocumentWriter> m_writer;
 
         // A reference to actual request used to create the data source.
         // This should only be used by the resourceLoadDelegate's
@@ -242,7 +248,6 @@ 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