This is a monster patch that turns all EventTargets into GC-allocated
PlatformObjects. Their C++ wrapper classes are removed, and the LibJS
garbage collector is now responsible for their lifetimes.
There's a fair amount of hacks and band-aids in this patch, and we'll
have a lot of cleanup to do after this.
Previously it would accept any DOMString, as we didn't support enums at
the time. Now it will only accept what's specified in the
DOMParserSupportedType enum.
This also adds spec comments to DOMParser::parse_from_string.
This allows you to invoke the HTML document parser and retrieve a
document as though it was loaded as a web page, minus any scripting
ability.
This does not currently support XML parsing.
This is used by YouTube (or more accurately, Web Components Polyfills)
to polyfill templates.
