Bug 970076 - Set preferred video colour format for OMX on Android 4.2 and 4.3. r=doublec, a=sledru

Android 4.2 introduced some relatively major changes in the way that Android
negotiates its output colour format. This was fixed on 4.4 KitKat in bug 953394.
This patch just lets Android versions 4.2 and 4.3 use the same fix.
Bug 969382. r=jorendorff, a=abillings
Bug 968084 - Context menu doesn't appear on list entries in Top Sites section. r=margaret, a=sledru
Bug 965361 - Show firefox watermark when you hide all panels in about:home. r=lucasr, a=sledru
Bug 974496 - Enable sync promo banner. r=bnicholson, a=sledru
Bug 965550 - Tab stip doesn't touch scroll if last tab is partially visible. r=mbrubeck, a=sledru