The University of California at Berkeley has labored to enroll more Black and Latino students in the quarter century since the state barred the consideration of race or ethnicity in its admissions. Still, those groups remain underrepresented at the renowned public university here on the eastern shore of the San Francisco Bay. The gap is huge for Latino students. They account for 55 percent of California’s public school students, state data show, but 19 percent of UC-Berkeley undergraduates.