docs(browser-setup): add notes about multiCapabilities

Author: juliemr

docs/browser-setup.md

@@ -37,6 +37,21 @@ capabilities: {
 ```
 If running with chromeOnly and chromeOptions together, chromeOptions.args and chromeOptions.extensions are required due to [Issue 6627](https://code.google.com/p/selenium/issues/detail?id=6627&thanks=6627&ts=1385488060) of selenium-webdriver currently(@2.37.0). So in order to avoid the issue, you may simply set them(or one of them) to an empty array.
 
+Testing against multiple browsers
+---------------------------------
+
+If you would like to test against multiple browsers at once, use the multiCapabilities configuration option.
+
+```javascript
+multiCapabilities: [{
+  'browserName': 'firefox'
+}, {
+  'browserName': 'chrome'
+}]
+```
+
+Protractor will run tests in parallel against each set of capabilities. Please note that if multiCapabilities is defined, the runner will ignore the `capabilities` configuration.
+
 PhantomJS
 -------------------------------------
 In order to test locally with [PhantomJS](http://phantomjs.org/), you'll need to either have it installed globally, or relative to your project. For global install see the [PhantomJS download page](http://phantomjs.org/download.html). For relative install run: `npm install --save-dev phantomjs`.