The ornamental design for a chairarm, as shown and described.
FIG. 1 is a perspective view showing the front, left side and top of a chair arm which forms my new design, the broken lines of a chair and an arm pad being for illustrative purposes only and forming no part of my design;
FIG. 2 is an enlarged left side elevational view thereof;
FIG. 3 is an enlarged top plan view thereof;
FIG. 4 is an enlarged right side elevational view thereof;
FIG. 5 is an enlarged bottom plan view thereof;
FIG. 6 is an enlarged front elevational view thereof;
FIG. 7 is an enlarged rear elevational view thereof; and,
FIG. 8 is an enlarged perspective view showing the front, left side and top thereof.