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// Returns a Promise that gets resolved with `event.data` when `window` receives from `source` a
// "message" event whose `event.data.type` matches the string `message_data_type`.
function getMessageData(message_data_type, source) {
return new Promise(resolve => {
function waitAndRemove(e) {
if (e.source != source || !e.data || e.data.type != message_data_type)
return;
window.removeEventListener("message", waitAndRemove);
resolve(e.data);
}
window.addEventListener("message", waitAndRemove);
});
}
// A helper that simulates user activation on the current frame if `activate` is true, then posts
// `message` to `frame` with the target `origin` and specified `capability` to delegate. This helper
// awaits and returns a Promise fulfilled with the result message sent in reply from `frame`.
// However, if the `postMessage` call fails, the helper returns a Promise rejected with the
// exception.
async function postCapabilityDelegationMessage(frame, message, origin, capability, activate) {
let result_promise = getMessageData("result", frame);
if (activate)
await test_driver.bless();
let postMessageOptions = {targetOrigin: origin};
if (capability)
postMessageOptions["delegate"] = capability;
try {
frame.postMessage(message, postMessageOptions);
} catch (exception) {
return Promise.reject(exception);
}
return await result_promise;
}
// Returns the name of a capability for which `postMessage` delegation is supported by the user
// agent, or undefined if no such capability is found.
async function findOneCapabilitySupportingDelegation() {
const capabilities = ["fullscreen", "payment", "display-capture"];
for (let i = 0; i < capabilities.length; i++) {
try {
await postCapabilityDelegationMessage(window, "any_message", "/", capabilities[i], false);
assert_unreached();
} catch (exception) {
if (exception.name != "NotSupportedError")
return capabilities[i];
// Ignore all other exceptions to continue searching through the list.
}
};
return undefined;
}