  We calculate the pion-pion elastic scattering phase shifts for pion masses
from the chiral limit to values of interest for lattice studies. At low
energies, we use the standard Chiral Perturbation Theory expressions to one and
two loops. In addition, we study the phase shifts mass dependence in the
resonance region by means of dispersion theory in the form of unitarized Chiral
Perturbation Theory and the Inverse Amplitude Method. We pay particular
attention to the case when resonances are close to threshold, illustrating the
different behavior between scalar and vector resonances. We also provide the
estimation of uncertainties, which are dominated by those of the O(p^6) chiral
parameters.
