DevTools: normalize the onResize/doResize usage, drive-by sidebar scroller fix.

R=dgozman@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=165941

Review URL: https://codereview.chromium.org/137143016

git-svn-id: svn://svn.chromium.org/blink/trunk@166008 bbb929c8-8fbe-4397-9dbb-9b2b20218538