wm: Initialize an uninitialized variable in event_loop_test.
wm: Initialize an uninitialized variable in event_loop_test.

The bug was introduced by 1adf0f63.  I was (un)lucky and
always got 0 when running this locally, I guess. :-(

BUG=none
TEST=ran them

Review URL: http://codereview.chromium.org/3150005

joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager,joshfire/chromiumos-platform-window_manager