Add Japanese to fallback fonts

On devices with adequate space, add MTLmr3m.ttf (Japanese) to the set
of fallback fonts. By default, DroidSansFallback (Chinese) is given
priority over MTLmr3m. If the locale is changed to Japanese, the
priority is reversed.

Bug: 6272763
Change-Id: I785a927d6dff0206aa9a670c51fdad76e219fc97