Google launched a “web clipboard” for copy & paste in Google Docs. This new clipboard temporarily stores items you’ve copied in the cloud, then allows you to paste them with proper formatting into other Google Docs. This web clipboard lets you copy content between documents, spreadsheets and presentations more easily and with improved fidelity. Note that while items in your web clipboard are available across browsers and across sessions, they do expire after a month. It seems to be an implementation of Google Cloudboard, an online clipboard that should help you copy content between Google services like Gmail, Google Calendar or Google Docs. More inforation on Google's help article titled ‘Text editing: Copying and pasting in Google Docs’.