chrome/test/chromedriver/extension/background.js

// Copyright (c) 2013 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.

/*
 * Checks for an extension error that occurred during the asynchronous call.
 * If an error occurs, will invoke the error callback and throw an exception.
 *
 * @param {function(!Error)} errCallback The callback to invoke for error
 *     reporting.
 */
function checkForExtensionError(errCallback) {
  if (typeof(chrome.extension.lastError) != 'undefined') {
    var error = new Error(chrome.extension.lastError.message);
    errCallback(error);
    throw error;
  }
}

/**
 * Captures a screenshot of the visible tab.
 *
 * @param {function(string)} callback The callback to invoke with the base64
 *     encoded PNG.
 * @param {function(!Error)} errCallback The callback to invoke for error
 *     reporting.
 */
function captureScreenshot(callback, errCallback) {
  chrome.tabs.captureVisibleTab({format:'png'}, function(dataUrl) {
    if (chrome.extension.lastError &&
        chrome.extension.lastError.message.indexOf('permission') != -1) {
      var error = new Error(chrome.extension.lastError.message);
      error.code = 103;  // kForbidden
      errCallback(error);
      return;
    }
    checkForExtensionError(errCallback);
    var base64 = ';base64,';
    callback(dataUrl.substr(dataUrl.indexOf(base64) + base64.length))
  });
}

/**
 * Launches an app with the specified id.
 *
 * @param {string} id The ID of the app to launch.
 * @param {function()} callback Invoked when the launch event is complete.
 * @param {function(!Error)} errCallback The callback to invoke for error
 *     reporting.
 */
function launchApp(id, callback, errCallback) {
  chrome.management.launchApp(id, function() {
    checkForExtensionError(errCallback);
    callback();
  });
}