Chrome has recently added support for protocol handlers, so that you can associate Gmail with mailto: links and Google Calendar with webcal: links. Now, when you visit Google Calendar using latest Chrome, you'll probably notice an infobar that asks you to "allow Google Calendar to open all web calendar links".
The infobar from Google Calendar requests your permission to associate the webcal: protocol with the application.
To edit the protocol handlers in Google Chrome, open a new tab and paste in the address bar: chrome://settings/handlers (you can also go to Options, select Under the hood, click Content settings and then click Manage handlers).
"Webcal is an unofficial Uniform Resource Identifier scheme for accessing iCalendar files. Webcal was initiated for use with the Apple iCal application and has become a common de facto standard for accessing iCalendar formatted files via WebDAV. It is not an official URI scheme, such as http and ftp, as registered with IANA. The Webcal protocol prefix is used to trigger an external protocol handler which is passed the URL of the .ics file rather than being passed the downloaded contents of the file, in much the same way feed is sometimes used to trigger external RSS readers. The idea is that with this protocol prefix the target file should be subscribed to rather than imported into the calendar application as would happen with a simple download.," Wikipedia