DevTools: Update file icon upon renaming.

R=pfeldman@chromium.org, pfeldman
BUG=271031

Review URL: https://codereview.chromium.org/25724012

git-svn-id: svn://svn.chromium.org/blink/trunk@159455 bbb929c8-8fbe-4397-9dbb-9b2b20218538