Have EditCommand classes deal with Document references, not pointers

Source/core/editing/UnlinkCommand.h

Index: Source/core/editing/UnlinkCommand.h
diff --git a/Source/core/editing/UnlinkCommand.h b/Source/core/editing/UnlinkCommand.h
index 6295d60ee1754efc5969f1514b825e64239ad7bc..d6b8d17bd286fdff2d4a5f207fe02147c0379386 100644
--- a/Source/core/editing/UnlinkCommand.h
+++ b/Source/core/editing/UnlinkCommand.h
@@ -32,13 +32,13 @@ namespace WebCore {
 
 class UnlinkCommand : public CompositeEditCommand {
 public:
-    static PassRefPtr<UnlinkCommand> create(Document* document)
+    static PassRefPtr<UnlinkCommand> create(Document& document)
     {
         return adoptRef(new UnlinkCommand(document));
     }
 
 private:
-    explicit UnlinkCommand(Document*);
+    explicit UnlinkCommand(Document&);
 
     virtual void doApply();
     virtual EditAction editingAction() const { return EditActionUnlink; }