Better support for the case of typed arrays inheriting from other typed arrays.

lib/dom/scripts/generator.py

Index: lib/dom/scripts/generator.py
diff --git a/lib/dom/scripts/generator.py b/lib/dom/scripts/generator.py
index 8d72a6c024459201352f46a8d717b078d2417b26..a5bf05c5477381af7dbf4f0ab393e21c145a7b97 100644
--- a/lib/dom/scripts/generator.py
+++ b/lib/dom/scripts/generator.py
@@ -108,10 +108,26 @@ def MaybeTypedArrayElementType(interface):
   """
   # Typed arrays implement ArrayBufferView and List<T>.
   for parent in interface.parents:
-    if  parent.type.id == 'ArrayBufferView':
+    if parent.type.id == 'ArrayBufferView':
       return MaybeListElementType(interface)
   return None
 
+def MaybeTypedArrayElementTypeInHierarchy(interface, database):
+  """Returns the typed array element type, or None in interface is not a
+  TypedArray.  Checks the whole parent hierarchy.
+  """
+  element_type = MaybeTypedArrayElementType(interface)
+  if element_type:
+    return element_type
+  for parent in interface.parents:
+    if database.HasInterface(parent.type.id):
+      parent_interface = database.GetInterface(parent.type.id)
+      element_type = MaybeTypedArrayElementType(parent_interface)
+      if element_type:
+        return element_type
+
+  return None
+
 def MakeNativeSpec(javascript_binding_name):
   if javascript_binding_name in _frog_dom_custom_native_specs:
     return _frog_dom_custom_native_specs[javascript_binding_name]