Use FrozenArray<SpeechRecognitionResult> and remove SpeechRecognitionResultList

[saschanaz]

Related 2013 discussion: https://lists.w3.org/Archives/Public/public-speech-api/2013Feb/0011.html

There was a previous attempt to remove SpeechRecognitionResultList but was reverted because Web IDL forbids attributes to return sequences.

The type of the attribute, after resolving typedefs, must not be a nullable or non-nullable version of any of the following types:

• a sequence type
• a dictionary type
• a record type
• a union type that has a nullable or non-nullable sequence type, dictionary, or record as one of its flattened member types

Attributes still can use FrozenArray which is also represented by JS native array object.

[foolip]

The compat risk here is the item method, which a plain Array doesn't have. Content in the wild might be using it, but if multiple implementers would like to simplify this, then we could add a use counter in Chrome and see if there's much usage.

[foolip]

See also https://www.w3.org/Bugs/Public/show_bug.cgi?id=30009.

[foolip]

Since SpeechRecognitionResultList has now shipped in Safari 14.1, I think we should not change this, it's just not worth it.