Refactoring: Simplify DocumentWriter by reorganizing its lifetime.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index e55ea85204d0fb7c4ef4e951607fd3d934be500a..bfc8d57e34b153a1d578b7852dfdcfcb86121a5b 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -2141,7 +2141,7 @@ void Document::cancelParsing()
     explicitClose();
 }
 
-void Document::implicitOpen()
+PassRefPtr<DocumentParser> Document::implicitOpen()
 {
     cancelParsing();
 
@@ -2159,6 +2159,8 @@ void Document::implicitOpen()
     m_parser = createParser();
     setParsing(true);
     setReadyState(Loading);
+
+    return m_parser;
 }
 
 HTMLElement* Document::body() const