DevTools: [Elements] Fix statusbar width computation to avoid breadcrumbs wrapping

The Settings button has never contributed to the statusbar width
when computing the breadcrumbs sizes.

R=pfeldman, vsevik
BUG=254927

Review URL: https://chromiumcodereview.appspot.com/18174003

git-svn-id: svn://svn.chromium.org/blink/trunk@153227 bbb929c8-8fbe-4397-9dbb-9b2b20218538