1 files changed, 50 insertions, 0 deletions
diff --git a/remote/cdp/domains/content/Emulation.sys.mjs b/remote/cdp/domains/content/Emulation.sys.mjs
new file mode 100644
index 0000000000..41bb0c76ea
--- /dev/null
+++ b/remote/cdp/domains/content/Emulation.sys.mjs
@@ -0,0 +1,50 @@
+/* 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";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AnimationFramePromise: "chrome://remote/content/shared/Sync.sys.mjs",
+});
+
+export class Emulation extends ContentProcessDomain {
+  // commands
+
+  /**
+   * Internal methods: the following methods are not part of CDP;
+   * note the _ prefix.
+   */
+
+  /**
+   * Waits until the viewport has reached the new dimensions.
+   */
+  async _awaitViewportDimensions({ width, height }) {
+    const win = this.content;
+    let resized;
+
+    // Updates for background tabs are throttled, and we also we have to make
+    // sure that the new browser dimensions have been received by the content
+    // process. As such wait for the next animation frame.
+    await lazy.AnimationFramePromise(win);
+
+    const checkBrowserSize = () => {
+      if (win.innerWidth === width && win.innerHeight === height) {
+        resized();
+      }
+    };
+
+    return new Promise(resolve => {
+      resized = resolve;
+
+      win.addEventListener("resize", checkBrowserSize);
+
+      // Trigger a layout flush in case none happened yet.
+      checkBrowserSize();
+    }).finally(() => {
+      win.removeEventListener("resize", checkBrowserSize);
+    });
+  }
+}