Match dispatchEvent return contract on dispatchTrustedEvent (#56761)

Summary:
Pull Request resolved: #56761

Aligns `dispatchTrustedEvent` and the underlying `[INTERNAL_DISPATCH_METHOD_KEY]` "protected" symbol method on `EventTarget` with the public `EventTarget.dispatchEvent` contract: both now return `boolean` (`!event.defaultPrevented`) instead of `void`, so callers can tell whether the event's default action was canceled.

Existing call sites ignore the return value, so this is a non-breaking widening.

Changelog: [Internal]

Reviewed By: javache

Differential Revision: D104651715

fbshipit-source-id: 0cc837adb705fc3b34ee4363cd5873176dac25cb

Author: rubennorte

packages/react-native/src/private/webapis/dom/events/EventTarget.js

@@ -243,11 +243,14 @@ export default class EventTarget {
   }
 
   /**
-   * This is "protected" method to dispatch trusted events.
+   * This is "protected" method to dispatch trusted events. Mirrors the
+   * `dispatchEvent` return contract: returns `false` if the event was
+   * canceled (i.e. `event.defaultPrevented`), otherwise `true`.
    */
   // $FlowExpectedError[unsupported-syntax]
-  [INTERNAL_DISPATCH_METHOD_KEY](event: Event): void {
+  [INTERNAL_DISPATCH_METHOD_KEY](event: Event): boolean {
     dispatch(this, event);
+    return !event.defaultPrevented;
   }
 }
 

packages/react-native/src/private/webapis/dom/events/internals/EventTargetInternals.js

@@ -48,15 +48,17 @@ export const INTERNAL_DISPATCH_METHOD_KEY: symbol = Symbol(
 );
 
 /**
- * Dispatches a trusted event to the given event target.
+ * Dispatches a trusted event to the given event target. Mirrors the
+ * `dispatchEvent` method on `EventTarget`: returns `false` if the event
+ * was canceled (i.e. `event.defaultPrevented`), otherwise `true`.
  *
  * This should only be used by the runtime to dispatch native events to
  * JavaScript.
  */
 export function dispatchTrustedEvent(
   eventTarget: EventTarget,
   event: Event,
-): void {
+): boolean {
   setIsTrusted(event, true);
 
   // $FlowExpectedError[prop-missing]