The following IDL files in //third_party/WebKit/Source/modules/webusb have problematic declarations:

USBAlternateInterface.idl:
    readonly attribute sequence<USBEndpoint> endpoints;

USBConfiguration.idl:
    readonly attribute sequence<USBInterface> interfaces;

USBDevice.idl:
    readonly attribute sequence<USBConfiguration> configurations;

USBInterface.idl:
    readonly attribute sequence<USBAlternateInterface> alternates;

USBIsochronousInTransferResult.idl:
    readonly attribute sequence<USBIsochronousInTransferPacket> packets;

USBIsochronousOutTransferResult.idl:
    readonly attribute sequence<USBIsochronousOutTransferPacket> packets;

https://heycam.github.io/webidl/#idl-sequence explicitly states that "Sequences must not be used as the type of an attribute or constant", and the WebUSB spec follows that by using FrozenArrays for attributes: https://github.com/WICG/webusb/commit/3a7cf63b7679971515563980e08c7987a373562b

We'd like to fix all occurrences of invalid attribute types in order to make the IDL compiler reject them in the future.