This adds support for async iterators of the form:
async iterable<value_type>;
async iterable<value_type>(/* arguments... */);
It does not yet support the value pairs of the form:
async iterable<key_type, value_type>;
async iterable<key_type, value_type>(/* arguments... */);
Async iterators have an optional `return` data property. There's not a
particularly good way to know what interfaces implement this property.
So this adds a new extended attribute, DefinesAsyncIteratorReturn, which
interfaces can use to declare their support.
There's a bit of a UTF-8 assumption with this change. But nearly every
caller of these methods were immediately creating a String from the
resulting ByteString anyways.
This fixes the frame-ancestors WPT tests from crashing when an iframe
is blocked from loading. This is because it would get an undefined
location.href from the cross-origin iframe, which causes a crash as it
expects it to be there.
In the case, where IDL enums start with a character, that is an invalid
start character for C++ identifiers (e.g. a number), the C++ generaion
for enums fails. An example would be "2d" see #3788
Previously the IDL Parser Complained, that a type with the name ''
(an empty string) couldn't be found. It wasn't that easy to see the
mistake, as the not named type is printed without '' around it, so the
message seemed to miss a type. This now catches this specify error
earlier and reports it cleanly to the user. An example of this
occurring would be ''typedef A (B or //FIXME: C )
This allows us to specify multiple base paths to look for imported IDL
files in. This will allow us to import IDL files from sources and from
the Build directory (i.e. for generated IDL files).
