Implement widget ReceiveTerminate capability

Signed-off-by: Pauli Virtanen <pav@iki.fi>

src/components/views/elements/AppTile.js

@@ -344,10 +344,18 @@ export default class AppTile extends React.Component {
      * @returns {Promise<*>} Resolves when the widget is terminated, or timeout passed.
      */
     _endWidgetActions() {
+        let promise;
+
+        if (this._hasCapability('m.receive_terminate')) {
+            // Wait for widget to terminate within a timeout
             const timeout = 2000;
             const messaging = ActiveWidgetStore.getWidgetMessaging(this.props.app.id);
+            promise = Promise.race([messaging.terminate(), sleep(timeout)]);
+        } else {
+            promise = Promise.resolve();
+        }
 
-        return Promise.race([messaging.terminate(), sleep(timeout)]).finally(() => {
+        return promise.finally(() => {
             // HACK: This is a really dirty way to ensure that Jitsi cleans up
             // its hold on the webcam. Without this, the widget holds a media
             // stream open, even after death. See https://github.com/vector-im/riot-web/issues/7351

src/utils/WidgetUtils.js

@@ -420,6 +420,7 @@ export default class WidgetUtils {
         if (WidgetType.JITSI.matches(appType)) {
             capWhitelist.push(Capability.AlwaysOnScreen);
         }
+        capWhitelist.push(Capability.ReceiveTerminate);
 
         return capWhitelist;
     }

src/widgets/WidgetApi.ts

@@ -23,6 +23,7 @@ export enum Capability {
     Screenshot = "m.capability.screenshot",
     Sticker = "m.sticker",
     AlwaysOnScreen = "m.always_on_screen",
+    ReceiveTerminate = "m.receive_terminate",
 }
 
 export enum KnownWidgetActions {