Docs on how to install tools for iOS buildbot testing

site/dev/testing/ios.md

+Testing on iOS
+==============
+Before setting Skia up for automated testing from the command line, please
+follow the instructions to run Skia tests (*dm*, *nano-bench*) with the
+mainstream iOS tool chain. See the [quick start guide for ios](../../user/quick/ios).
+
+iOS doesn't lend itself well to compiling and running from the command line.
+Below are instructions on how to install a set of tools that make this possible.
+To see how they are used in automated testing please see the bash scripts
+used by the buildbot recipes: <https://github.com/google/skia/tree/master/platform_tools/ios/bin>.
+
+Installation
+------------
+The key tools are
+
+* libimobiledevice <http://www.libimobiledevice.org/>, <https://github.com/libimobiledevice/libimobiledevice>
+
+* ios-deploy <https://github.com/phonegap/ios-deploy>
+
+Follow these steps to install them:
+
+* Install Brew at <http://brew.sh/>
+* Install *libimobiledevice*
+  (Note: All these are part of the *libimobiledevice* project but packaged/developed
+  under different names. The *cask* extension to *brew* is necessary to install
+  *osxfuse* and *ifuse*, which allows to mount the application directory on an iOS device).
+```
+brew install libimobiledevice
+brew install ideviceinstaller
+brew install caskroom/cask/brew-cask
+brew install Caskroom/cask/osxfuse
+brew install ifuse
+```
+* Install node.js and ios-deploy
+```
+$ brew update
+$ brew install node
+$ npm install ios-deploy
+```