The release notes are now available! https://releasenotes.docs.salesforce.com/en-us/spring17/release-notes/salesforce_release_notes.htm
Visualforce Button to Close A Window
Easy to do with a little JavaScript! <apex:commandbutton onClick=”window.top.close();” value=”Close”/>
Visualforce Date Popup
If you work with Visualforce and the first field on your page is a date you’ll notice that when the page loads it’ll automatically open the date picker which is often not desirable. To fix this simply place this Javascript on your page: <Script> function setFocusOnLoad() {} </Script>