Content Translation allows users to start a new translation when they are reading a Wikipedia article that is not available in their usual languages (shown as grey links). A panel is shown for the user to start the translation:
The grey area at the bottom part of the panel is intended to cover it from edge to edge. However, due to the way padding is applied, there is a white space surrounding the grey area. This was not the case before, so a regression may have resulted in the extra padding on the dialog.