DevTools: Fix frontend compilation errors uncovered by r184188

R=dgozman@chromium.org, pfeldman@chromium.org, dgozman

Review URL: https://codereview.chromium.org/671913006

git-svn-id: svn://svn.chromium.org/blink/trunk@184240 bbb929c8-8fbe-4397-9dbb-9b2b20218538