The ornamental design for a massagechair, as shown and described.
FIG. 1 is a perspective view of a massage chair showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is another perspective view thereof with a pillow placed thereon.
A bottom view thereof is omitted since it does not contain ornamental features. The heavy broken line showing of stitch lines in FIGS. 1, 2 and 4-7 forms portions of the claimed design, while the light broken line portions of the massage chair in in FIGS. 1-7 represent unclaimed portions of the claimed design and form no part thereof.