Reland Track the active ExtensionKeybindingRegistry and make it available to EventRewriter.

chrome/test/data/extensions/api_test/keybinding/chromeos_conversions/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.
+
+// A list of all commands sorted in expected order.
+var expectedCommands = [
+  'Search-Shift-Left',
+  'Search-Shift-Up',
+  'Search-Shift-Right',
+  'Search-Shift-Down'
+];
+
+chrome.commands.onCommand.addListener(function (command) {
+  if (expectedCommands[0] != command)
+    chrome.test.notifyFail('Unexpected command: ' + command);
+  expectedCommands.splice(0, 1);
+  if (expectedCommands.length == 0)
+    chrome.test.notifyPass();
+});
+
+chrome.test.notifyPass();