There are various bugs in the WebIDL blocks:

> [Supplemental] interface Document {
>   NamedFlow getFlowByName(DOMString name);
>   NamedFlowCollection getNamedFlows();
> };

'[Supplemental]' should be 'partial'.

> interface NamedFlowCollection {
>     readonly attribute unsigned long length;
>     caller getter NamedFlow item (in unsigned long index);
> }

Trailing semicolon is missing.

'caller' should not be used, as it should only be used for legacy features (document.all). See <http://dev.w3.org/2006/webapi/WebIDL/#idl-legacy-callers>.

The specification does not list the 'supported property indices', as required by the WebIDL specification (<http://dev.w3.org/2006/webapi/WebIDL/#idl-indexed-properties>).

Furthermore, as item() can return null, the return type must be 'NamedFlow?', including the question mark.

'in' is also no longer supported.

> [Supplemental] interface Element {
>     readonly attribute DOMString regionOverflow;
>     getter Range[] getRegionFlowRanges();
> };

Again, 'partial'.

'getter's must take exactly one argument (either unsigned long or DOMString). In fact, this should probably be

|     readonly attribute Range[] regionFlowRanges;

as there doesn't seem to be a compelling reason to use a function.

Finally, a normative reference to the WebIDL specification is missing, which strictly speaking means that these snippets are meaningless.