DevTools: Fix modularization of HelpScreen derivatives

- HelpScreenUntilReload depends on DebuggerModel
- RemoteDebuggingTerminatedScreen does not depend on anything


R=aandrey, eustas, pfeldman, vsevik

Review URL: https://codereview.chromium.org/136443004

git-svn-id: svn://svn.chromium.org/blink/trunk@165280 bbb929c8-8fbe-4397-9dbb-9b2b20218538