1 files changed, 57 insertions, 0 deletions
diff --git a/remote/cdp/domains/content/Input.sys.mjs b/remote/cdp/domains/content/Input.sys.mjs
new file mode 100644
index 0000000000..e7a6ffc709
--- /dev/null
+++ b/remote/cdp/domains/content/Input.sys.mjs
@@ -0,0 +1,57 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import { ContentProcessDomain } from "chrome://remote/content/cdp/domains/ContentProcessDomain.sys.mjs";
+
+export class Input extends ContentProcessDomain {
+  constructor(session) {
+    super(session);
+
+    // Internal id used to track existing event handlers.
+    this._eventId = 0;
+
+    // Map of event id -> event handler promise.
+    this._eventPromises = new Map();
+  }
+
+  /**
+   * Internal methods: the following methods are not part of CDP;
+   * note the _ prefix.
+   */
+
+  /**
+   * Add an event listener in the content page for the provided eventName.
+   * This method will return a unique handler id that can be used to wait
+   * for the event.
+   *
+   * Example usage from a parent process domain:
+   *
+   *   const id = await this.executeInChild("_addContentEventListener", "click");
+   *   // do something that triggers a click in content
+   *   await this.executeInChild("_waitForContentEvent", id);
+   */
+  _addContentEventListener(eventName) {
+    const eventPromise = new Promise(resolve => {
+      this.chromeEventHandler.addEventListener(eventName, resolve, {
+        mozSystemGroup: true,
+        once: true,
+      });
+    });
+    this._eventId++;
+    this._eventPromises.set(this._eventId, eventPromise);
+    return this._eventId;
+  }
+
+  /**
+   * Wait for an event listener added via `addContentEventListener` to be fired.
+   */
+  async _waitForContentEvent(eventId) {
+    const eventPromise = this._eventPromises.get(eventId);
+    if (!eventPromise) {
+      throw new Error("No event promise found for id " + eventId);
+    }
+    await eventPromise;
+    this._eventPromises.delete(eventId);
+  }
+}