Implement UI automation on the Mac.

Code is untested.  From gChat:
  me: do you have a good test I can use to make sure mac impl of
    ui_controls for sending events works OK?  Or would you prefer I send
    you CLs to play with and we iterate by hand?
  Joe: I would like the CL to play with to see if I can get it to work
    with the code I wrote

Warning to Joe: mouse moved events currently use the Mac coordinate
frame (0,0 is bottom-left not top-left). That's easy to switch; I'd
like to do whatever is easiest to get WebDriver working.

BUG=26102

Review URL: http://codereview.chromium.org/1701006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@46005 0039d316-1c4b-4281-b951-d872f2087c98
18 files changed