Fix background page externs.
Fix background page externs.

codex8/text-app,zkendall/WordBinder,codex8/text-app,modulexcite/text-app,modulexcite/text-app,l3dlp/text-app,l3dlp/text-app,modulexcite/text-app,codex8/text-app,zkendall/WordBinder,zkendall/WordBinder,l3dlp/text-app