Bug 1056457 - Remove batch changes in selection carets. r=roc
Bug 1057256 - Part 1 - Remove NS_ENSURE_TRUE in SelectionCarets.cpp. r=roc

Remove NS_ENSURE_TRUE and NS_ENSURE_TRUE_VOID since they are deprecated,
and we do not need to print log in plain null pointer check.
Bug 1057256 - Part 2 - Add null pointer check for touch and selection carets. r=roc

TouchCaret::IsDisplayable() contains more null pointer check. It covers
what's original there in TouchCaret::HandleEvent().
Bug 1057256 - Part 3 - Make touch caret handle events before selection carets. r=roc