After the DisplayList is enabled by default, remove the flag [here](https://github.com/flutter/engine/blob/dfa7f1995f0f4952f06ba7a1bd35e0b7e4af542f/common/settings.h#L169), and clean up the code using SkPicture that becomes dead as a result.
