Fix tracing for WebDriver#getPageSource

The tracing for sending the `getPageSource` command instead identified the command as `getAllWindowHandles`

Signed-off-by: Daniel Davison <daniel.jj.davison@gmail.com>

Author: JustinTulloss

javascript/webdriver/webdriver.js

@@ -766,7 +766,7 @@ webdriver.WebDriver.prototype.getAllWindowHandles = function() {
 webdriver.WebDriver.prototype.getPageSource = function() {
   return this.schedule(
       new webdriver.Command(webdriver.CommandName.GET_PAGE_SOURCE),
-      'WebDriver.getAllWindowHandles()');
+      'WebDriver.getPageSource()');
 };