Revert 255368 "Clean up WindowEventDispatcher some more."

> Clean up WindowEventDispatcher some more.
> 
> . Eliminate the implementation of LayerAnimationObserver. It seems no one expects WED to be a LAO anymore.
> . Remove WindowTreeHostDelegate. This involves moving some of the functions to WTH, removing some completely, and moving the remainder to the WED public API. A little icky for now, but I plan to take a pass on cleaning up WED's public API once I get it pared down.
> . window_tree_host_x11_unittest provided an implementation of WTHD that was not WED. This is not a valid situation now since various functions in WTH now call directly through to WED. Replaced this with a simple EventHandler to test that events are being dispatched.
> 
> R=sky@chromium.org
> http://crbug.com/308843
> 
> Review URL: https://codereview.chromium.org/188223002

TBR=ben@chromium.org

Review URL: https://codereview.chromium.org/188843003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255399 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255399