Pfizer Inc. is joining with two Boston hospitals to test whether computerized patient records can be used in helping federal regulators detect dangerous drug side effects. Massachusetts General and Brigham and Women's hospitals are encouraging 30 of their doctors to report serious side effects to the Food and Drug Administration by making the reports part of their normal routine filling out electronic patient charts. If successful, the pilot program could point the way for increasing the number of side-effect reports filed and for improving their quality.