Revert 251382 "event-rewrite: Clean up how events are rewritten."

Revert 251382 "event-rewrite: Clean up how events are rewritten."

> event-rewrite: Clean up how events are rewritten.
> 
> Notable changes:
>  * Make the EventRewriter a MessagePumpObserver. This is necessary to make sure
>    that the event-rewrite happens before the event is dispatched.
>  * Move the EventRewriter in chrome/browser/chromeos (and in chromeos namespace),
>    since it does nothing on other platforms.
>  * Get rid of the event-rewrite code from ash, since it just adds an extra layer
>    of abstraction for no added value.
> 
> BUG=343639
> R=derat@chromium.org, sky@chromium.org, stevenjb@chromium.org
> 
> Review URL: https://codereview.chromium.org/165463002

This was causing the following check failure

[3943:3943:0214/135331:FATAL:event_rewriter.cc(858)] Check failed:
xievent->evtype == XI_ButtonPress || xievent->evtype == XI_ButtonRelease. 
Aborted (core dumped)

TBR=sadrul@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251433

[oshima, 2014-02-14 22:38:09]

Committed patchset #1 manually as r251433 (tree was closed).