Have Document::markers() return a reference

Source/core/dom/DocumentMarkerControllerTest.cpp

 /*
  * Copyright (c) 2013, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 33 matching lines @@
 
 using namespace WebCore;
 
 namespace {
 
 class DocumentMarkerControllerTest : public ::testing::Test {
 protected:
     virtual void SetUp() OVERRIDE;
 
     Document& document() const { return *m_document; }
-    DocumentMarkerController& markerController() const { return *m_document->markers(); }
+    DocumentMarkerController& markerController() const { return m_document->markers(); }
 
     PassRefPtr<Text> createTextNode(const char*);
     void markNodeContents(PassRefPtr<Node>);
     void setBodyInnerHTML(const char*);
 
 private:
     OwnPtr<DummyPageHolder> m_dummyPageHolder;
     Document* m_document;
 };
 
@@ skipping 107 matching lines @@
         RefPtr<Element> parent = toElement(document().body()->firstChild()->firstChild());
         markNodeContents(parent);
         EXPECT_EQ(1u, markerController().markers().size());
         setBodyInnerHTML("");
     }
     // No more reference to marked node.
     EXPECT_EQ(0u, markerController().markers().size());
 }
 
 }