events: Remove no-op events.

No-op events were used only in a test to terminate a message-loop. So remove
the no-op events related code from the API, and directly terminate the message
loop in the test instead.

BUG=none
R=oshima@chromium.org

Review URL: https://codereview.chromium.org/141793004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250030 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250030