add better cleanup support and error checking
add better cleanup support and error checking

levexis/full-page-screen-capture-chrome-extension,cinegen/full-page-screen-capture-chrome-extension,fdioajsf/full-page-screen-capture-chrome-extension,mrcoles/full-page-screen-capture-chrome-extension,modulexcite/full-page-screen-capture-chrome-extension,mrcoles/full-page-screen-capture-chrome-extension,levexis/full-page-screen-capture-chrome-extension,mrcoles/full-page-screen-capture-chrome-extension,jenghung/bugraker-chrome-plugin,modulexcite/full-page-screen-capture-chrome-extension,jenghung/bugraker-chrome-plugin,micahbrich/screenshot-chrome,fdioajsf/full-page-screen-capture-chrome-extension,fdioajsf/full-page-screen-capture-chrome-extension,modulexcite/full-page-screen-capture-chrome-extension,levexis/full-page-screen-capture-chrome-extension,jenghung/bugraker-chrome-plugin,micahbrich/screenshot-chrome,cinegen/full-page-screen-capture-chrome-extension,cinegen/full-page-screen-capture-chrome-extension,micahbrich/screenshot-chrome