Implements RLZ lib for iOS

Use the OS X implementation of the RlzValueStore and derive the machine
identifier from -[UIDevice identifierForVendor].

BUG=309629

Review URL: https://codereview.chromium.org/29873005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230429 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230429