DevTools: slight tweaking of step-into-selection feature
DevTools: slight tweaking of step-into-selection feature

This patch does a slight CSS tweaking related to step-into-selection
feature.

BUG=275661

Review URL: https://chromiumcodereview.appspot.com/23684038

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@157527 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs