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 6f6aa1f26a94ecabfb16cc4b7f83b79bbe850c21..5e4eaea40d30d8938e0b4c573abc82d5f5829a0f 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -2152,7 +2152,7 @@ void Document::cancelParsing()
     explicitClose();
 }
 
-void Document::implicitOpen()
+PassRefPtr<DocumentParser> Document::implicitOpen()
 {
     cancelParsing();
 
@@ -2170,6 +2170,8 @@ void Document::implicitOpen()
     m_parser = createParser();
     setParsing(true);
     setReadyState(Loading);
+
+    return m_parser;
 }
 
 HTMLElement* Document::body() const