Revert 172810 "Add a "forwarded" flag to usergesture tokens."

This had the unintended side effect of breaking websites,
so reverting this while we figure out a proper fix.

BUG=369963

> Add a "forwarded" flag to usergesture tokens.
> 
> Exposing this and using it in DOMTimer to check if a user gesture token
> should be forwarded allows for other ways of forwarding user gestures
> while still preventing a user gesture from being forwarded more than
> once.
> 
> BUG=354217
> 
> Review URL: https://codereview.chromium.org/258783004

TBR=mek@chromium.org

Review URL: https://codereview.chromium.org/264333002

git-svn-id: svn://svn.chromium.org/blink/trunk@173445 bbb929c8-8fbe-4397-9dbb-9b2b20218538