Always update screenshots for bookmarks

 Bug: 3425221
 Changes the call to updateScreenshot to take the Tab so that it
 can more intelligently determine if it needs to update the screenshot.
 Specifically, if it is an HTTP/HTTPS URL, we always update (for things
 like most visited), and if it is a bookmark we always update (users
 are free to bookmark file:// urls, for example)

Change-Id: I582284d612e77190404eb98de6ca8a0b21083ed1
1 file changed