This patch improves the user experience when using spatial navigation (enabled in https://codereview.chromium.org/13811041 and https://codereview.chromium.org/14110006 ):

- Dispatch onClick when pressing ENTER or SPACE on any element (not only input buttons as it was before the patch)
- Make HTMLElement focusable by spatnav if it has click or key events (before it could only navigate to links and form items). 

The changes are effective only if spatialNavigationEnabled pref is enabled.



BUG=

Review URL: https://chromiumcodereview.appspot.com/16959002

git-svn-id: svn://svn.chromium.org/blink/trunk@152930 bbb929c8-8fbe-4397-9dbb-9b2b20218538