Replace CursorList with RefVector<CursorData>.

Source/wtf/RefVector.h

Index: Source/wtf/RefVector.h
diff --git a/Source/wtf/RefVector.h b/Source/wtf/RefVector.h
index 1ba8c996e47373bca570bcf2afac02e8cde4ec5c..5117ce9cdb9a8d2875f4bf911defb2b92766f12d 100644
--- a/Source/wtf/RefVector.h
+++ b/Source/wtf/RefVector.h
@@ -19,6 +19,8 @@ public:
 
     const T& operator[](size_t i) const { return m_vector[i]; }
     T& operator[](size_t i) { return m_vector[i]; }
+    const T& at(size_t i) const { return m_vector.at(i); }
+    T& at(size_t i) { return m_vector.at(i); }
 
     bool operator==(const RefVector& o) const { return m_vector == o.m_vector; }
     bool operator!=(const RefVector& o) const { return m_vector != o.m_vector; }