Have Document::markers() return a reference

Source/core/editing/CompositeEditCommand.cpp

Index: Source/core/editing/CompositeEditCommand.cpp
diff --git a/Source/core/editing/CompositeEditCommand.cpp b/Source/core/editing/CompositeEditCommand.cpp
index 3b3ade0f3d9f22b07bacd384ee5f65d2800a7543..5c0fa47fc0e93a43a1e2b39a43d7192bbb4a5211 100644
--- a/Source/core/editing/CompositeEditCommand.cpp
+++ b/Source/core/editing/CompositeEditCommand.cpp
@@ -497,13 +497,13 @@ static void copyMarkers(const Vector<DocumentMarker*>& markerPointers, Vector<Do
 void CompositeEditCommand::replaceTextInNodePreservingMarkers(PassRefPtr<Text> prpNode, unsigned offset, unsigned count, const String& replacementText)
 {
     RefPtr<Text> node(prpNode);
-    DocumentMarkerController* markerController = document().markers();
+    DocumentMarkerController& markerController = document().markers();
     Vector<DocumentMarker> markers;
-    copyMarkers(markerController->markersInRange(Range::create(document(), node.get(), offset, node.get(), offset + count).get(), DocumentMarker::AllMarkers()), markers);
+    copyMarkers(markerController.markersInRange(Range::create(document(), node.get(), offset, node.get(), offset + count).get(), DocumentMarker::AllMarkers()), markers);
     replaceTextInNode(node, offset, count, replacementText);
     RefPtr<Range> newRange = Range::create(document(), node.get(), offset, node.get(), offset + replacementText.length());
     for (size_t i = 0; i < markers.size(); ++i)
-        markerController->addMarker(newRange.get(), markers[i].type(), markers[i].description());
+        markerController.addMarker(newRange.get(), markers[i].type(), markers[i].description());
 }
 
 Position CompositeEditCommand::positionOutsideTabSpan(const Position& pos)