[bindings] Avoid using custom binding for HTMLOptionsCollection.length attribute

Source/core/html/HTMLOptionsCollection.cpp

Index: Source/core/html/HTMLOptionsCollection.cpp
diff --git a/Source/core/html/HTMLOptionsCollection.cpp b/Source/core/html/HTMLOptionsCollection.cpp
index 1b9c61989d690657f43387ff68b19730de456912..e2724df1c867b37e43aeb5bc2dfd19795a94dab3 100644
--- a/Source/core/html/HTMLOptionsCollection.cpp
+++ b/Source/core/html/HTMLOptionsCollection.cpp
@@ -91,6 +91,8 @@ void HTMLOptionsCollection::setSelectedIndex(int index)
 
 void HTMLOptionsCollection::setLength(unsigned length, ExceptionState& exceptionState)
 {
+    if (length > HTMLSelectElement::maxSelectItems)
+        return;

[tkent, 2015/08/19 01:20:24]

It's inconsistent with the current behavior of HTMLSelectElement::length setter,
which clamps on the value to maxSelectItems.

Does Firefox still have the limitation of the number of items?  If so, how does
it work for length setters?

     toHTMLSelectElement(ownerNode()).setLength(length, exceptionState);
 }