WebUSB testing relies on the [WebUSB Testing API] which must be
provided by browsers under test.
In this test suite `resources/usb-helpers.js` detects and triggers
the API to be loaded as needed.
The Chromium implementation is provided by
`../resources/chromium/webusb-test.js` using [MojoJS].
Tests with the "-manual" suffix do not use the test-only interface and expect a
real hardware device to be connected. The specific characteristics of the device
are described in each test.
