Refactoring: Simplify DocumentWriter by reorganizing its lifetime.

Source/core/svg/graphics/SVGImage.cpp

Index: Source/core/svg/graphics/SVGImage.cpp
diff --git a/Source/core/svg/graphics/SVGImage.cpp b/Source/core/svg/graphics/SVGImage.cpp
index b248d0b787b4b37c1f827eda493e373dc30b27f9..c8231a1b40fd48ac641f074f5a01d72926e5eab6 100644
--- a/Source/core/svg/graphics/SVGImage.cpp
+++ b/Source/core/svg/graphics/SVGImage.cpp
@@ -355,7 +355,7 @@ bool SVGImage::dataChanged(bool allDataReceived)
         ASSERT(loader->activeDocumentLoader()); // DocumentLoader should have been created by frame->init().
         DocumentWriter* writer = loader->activeDocumentLoader()->beginWriting("image/svg+xml", "UTF-8");
         writer->addData(data()->data(), data()->size());
-        writer->end();
+        loader->activeDocumentLoader()->endWriting(writer);
         // Set the intrinsic size before a container size is available.
         m_intrinsicSize = containerSize();
     }