Sync some HTML interfaces with the spec

Source/core/html/VoidCallback.idl

Index: Source/core/html/VoidCallback.idl
diff --git a/Source/core/html/VoidCallback.idl b/Source/core/html/VoidCallback.idl
index 970113b02005cfa818e9197486bb7c1b1669cb82..daf58ab86b73b9e8ec513695dcfe9ae9b2517602 100644
--- a/Source/core/html/VoidCallback.idl
+++ b/Source/core/html/VoidCallback.idl
@@ -23,6 +23,10 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+// TODO(philipj): This callback interface was added for HTMLMediaElement's
+// addCuePoint() and removeCuePoint(), which briefly existed in 2007. It is no
+// longer used in HTML and should be moved to where it is used.
+
 callback interface VoidCallback {
     void handleEvent();
 };