Continue key propagation for extensions without any listeners to chrome.commands.onCommand.

chrome/test/data/extensions/api_test/keybinding/continue_propagation/background.js

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Keeps track of who should be receiving keystrokes sent:
+// The 'webPage' or the 'backgroundPage'.
+var expectedListener = 'webPage';
+
+function gotCommand(command) {
+  if (expectedListener == 'backgroundPage') {
+    expectedListener = 'webPage';
+    chrome.commands.onCommand.removeListener(gotCommand);
+    chrome.test.notifyPass();
+  } else {
+    chrome.test.notifyFail('Webpage expected keystroke, but sent to extension');
+  }
+}
+
+chrome.extension.onConnect.addListener(function(port) {
+  port.onMessage.addListener(function(message) {
+    if (expectedListener == 'webPage') {
+      expectedListener = 'backgroundPage';
+      chrome.commands.onCommand.addListener(gotCommand);
+      chrome.test.notifyPass();
+    } else {
+      chrome.test.notifyFail('Extension expected keystroke, but sent to' +
+          ' webpage');
+    }
+  });
+});
+
+chrome.test.notifyPass();