Converts an image to PNG before showing the Save As dialog. WebP is a new image format developed by Google. These images are small, but their format is not widely recognized yet. By converting the image to PNG, you will be able to use it in image editing programs, and/or upload it to online image hosting sites such as imgur. The extension has a low footprint: It does not use any memory or CPU unless you use it by clicking on the context menu option.
Via +Jeremy Seifert's comment on +Alex Hernandez's post
Adds the “Save Image As PNG” option to the context menu of images.