Due to Security Sandbox of the Webplayer we not able to send data directly from Unity Web Player on a domain other than the one hosting your .unity3d file. That’s why plugin use additional java script for sending the data.
And that’s why we not able to send data from the editor while we in the web player mode. Because in the web player mode Editor will emulate this restriction.
Here is small guide how to enable analytics data sending from the Web Player. One the Player Settings before building and choose Analytics template in the Web Player settings.
In case you want to use your own template, you need to connect the GoogleAnalyticsUnityPlugin.js script to your Web Player template. With can be founded at: Assets/WebPlayerTemplates/Analytics/js/GoogleAnalyticsUnityPlugin.js