Fix mouse wheel events not being modified correctly by sticky keys.

To increase code coverage, also test the actual sticky keys event dispatch
implementation.

BUG=320163
TEST=new tests

Review URL: https://codereview.chromium.org/79293002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236656 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236656
linux aura: Fix some more dragging issues.

Make sure capture happens properly when doing a drag. It is possible to reach
the code in X11WholeScreenMoveLoop::RunMoveLoop() from more than one place. So
do the capture in there.

BUG=317563
R=erg@chromium.org

Review URL: https://codereview.chromium.org/81713002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236657 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236657