[js] Introduce the SELENIUM_PROMISE_MANAGER environment variable, whi…

…ch can be

set to 0 to disable use of the promise manager.

Full details and motivation behind this change can be found in #2969

javascript/node/selenium-webdriver/CHANGES.md

@@ -16,6 +16,10 @@
   "moz:firefoxOptions" dictionary for Firefox-specific configuration values.
 * Extending the `selenium-webdriver/testing` module to support tests defined
   using generator functions.
+* The promise manager can be disabled by setting an enviornment variable:
+  `SELENIUM_PROMISE_MANAGER=0`. This is part of a larger plan to remove the
+  promise manager, as documented at
+  <https://github.com/SeleniumHQ/selenium/issues/2969>
 
 
 ### API Changes

javascript/node/selenium-webdriver/example/google_search.js

@@ -35,16 +35,14 @@
  *     node selenium-webdriver/example/google_search.js
  */
 
-var webdriver = require('..'),
-    By = webdriver.By,
-    until = webdriver.until;
+const {Builder, By, until} = require('..');
 
-var driver = new webdriver.Builder()
+var driver = new Builder()
     .forBrowser('firefox')
     .build();
 
-driver.get('http://www.google.com/ncr');
-driver.findElement(By.name('q')).sendKeys('webdriver');
-driver.findElement(By.name('btnG')).click();
-driver.wait(until.titleIs('webdriver - Google Search'), 1000);
-driver.quit();
+driver.get('http://www.google.com/ncr')
+    .then(_ => driver.findElement(By.name('q')).sendKeys('webdriver'))
+    .then(_ => driver.findElement(By.name('btnG')).click())
+    .then(_ => driver.wait(until.titleIs('webdriver - Google Search'), 1000))
+    .then(_ => driver.quit());

javascript/node/selenium-webdriver/index.js

@@ -594,7 +594,7 @@ class Builder {
    * __Note:__ this method is purely a convenience wrapper around
    * {@link #build()}.
    *
-   * @return {!promise.Promise<!webdriver.WebDriver>} A promise that will be
+   * @return {!promise.Thenable<!webdriver.WebDriver>} A promise that will be
    *    fulfilled with the newly created WebDriver instance once the browser
    *    has been fully initialized.
    * @see #build()