Mark DOMStringList.contains() as deprecated, add console warning.

Source/core/dom/DOMStringList.h

Index: Source/core/dom/DOMStringList.h
diff --git a/Source/core/dom/DOMStringList.h b/Source/core/dom/DOMStringList.h
index 3d3011907781e5fbfb6c0b00c081e68f820f078b..58c21130cd58d2abdcd1fc20469e611538ae2c17 100644
--- a/Source/core/dom/DOMStringList.h
+++ b/Source/core/dom/DOMStringList.h
@@ -52,6 +52,7 @@ public:
 
     // Implements the IDL.
     size_t length() const { return m_strings.size(); }
+    String anonymousIndexedGetter(unsigned index) const { return item(index); }
     String item(unsigned index) const;
     bool contains(const String& str) const;