1 files changed, 85 insertions, 0 deletions
diff --git a/testing/raptor/browsertime/utils/NetworkThrottlingUtils.js b/testing/raptor/browsertime/utils/NetworkThrottlingUtils.js
new file mode 100644
index 0000000000..8a0f78150e
--- /dev/null
+++ b/testing/raptor/browsertime/utils/NetworkThrottlingUtils.js
@@ -0,0 +1,85 @@
+/* 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/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  NetworkObserver:
+    "resource://devtools/shared/network-observer/NetworkObserver.sys.mjs",
+});
+
+/**
+ * The NetworkThrottler uses the dev tools NetworkObserver to provide api to throttle all network activity.
+ * This can be used to fix network conditions in browsertime pageload tests.
+ *
+ */
+
+// A minimal struct for onNetworkEvent handling
+class NetworkEventRecord {
+  addRequestPostData() {}
+  addResponseStart() {}
+  addSecurityInfo() {}
+  addEventTimings() {}
+  addResponseCache() {}
+  addResponseContent() {}
+  addServerTimings() {}
+  addServiceWorkerTimings() {}
+}
+
+class NetworkThrottler {
+  #devtoolsNetworkObserver;
+  #throttling;
+
+  constructor() {
+    this.#throttling = false;
+  }
+
+  destroy() {
+    this.stop();
+  }
+
+  start(throttleData) {
+    if (this.#throttling) {
+      console.error("NetworkThrottler already started");
+      return;
+    }
+
+    this.#devtoolsNetworkObserver = new lazy.NetworkObserver({
+      ignoreChannelFunction: this.#ignoreChannelFunction,
+      onNetworkEvent: this.#onNetworkEvent,
+    });
+
+    this.#devtoolsNetworkObserver.setThrottleData(throttleData);
+
+    this.#throttling = true;
+  }
+
+  stop() {
+    if (!this.#throttling) {
+      return;
+    }
+
+    this.#devtoolsNetworkObserver.destroy();
+    this.#devtoolsNetworkObserver = null;
+
+    this.#throttling = false;
+  }
+
+  #ignoreChannelFunction = channel => {
+    // Ignore chrome-privileged or DevTools-initiated requests
+    if (
+      channel.loadInfo?.loadingDocument === null &&
+      (channel.loadInfo.loadingPrincipal ===
+        Services.scriptSecurityManager.getSystemPrincipal() ||
+        channel.loadInfo.isInDevToolsContext)
+    ) {
+      return true;
+    }
+    return false;
+  };
+
+  #onNetworkEvent = (networkEvent, channel) => {
+    return new NetworkEventRecord(networkEvent, channel, this);
+  };
+}