Clicking on non-focusable elements should remove focus of the focused element in another frame.

This is a regression by [1].

As the CL description of [1] said, we should avoid early return in
FocusController::setFocusedElement. We'd like to continue to execute this
function if frame focus will be changed and there wll be no focused element.

[1] http://src.chromium.org/viewvc/blink?revision=161312&view=revision
BUG=334999
TEST=automated

Review URL: https://codereview.chromium.org/159983009

git-svn-id: svn://svn.chromium.org/blink/trunk@167070 bbb929c8-8fbe-4397-9dbb-9b2b20218538