Bug 941868 - Part 2: load and cache certain preloaded favicons on launch, and remove favicon from about:home's HTML content. r=mcomella
Bug 941868 - Part 3: don't evict built-in bitmaps, either. r=mcomella
Bug 941868 - Part 4: tidying and enforcing TabEvent non-null-tab constraint. r=mcomella
Bug 941868 - Part 5: don't fetch about:home's favicon later in the load cycle. r=mcomella