Bug 931843 - Part 0: tidy up constants in TopSitesGridItemView. r=kats
Bug 931843 - Part 1: generate smaller thumbnails. r=kats
Bug 931843 - Part 2: rewrite OnFaviconLoadedListeners to hold fewer references. r=bnicholson
Bug 931843 - Part 3: don't retain thumbnails. r=bnicholson