/analysis/field doesn't always handle custom attributes correctly

I've got some custom analysis Attribute implementations in my analysis chain with some other custom analysis components. I found that Solr's Analysis utility screen, powered by /field/analysis (FieldAnalysisRequestHandler subclassing AnalysisRequestHandlerBase) gave me exceptions for two reasons, both having to do with AnalysisRequestHandlerBase.ListBasedTokenStream:

• Custom implementations of standard Attributes (e.g. FlagsAttribute) would trigger an exception.
• Calling getAttribute (instead of addAttribute) in a TokenFilter constructor wouldn't find an attribute added by the input TokenStream.