In a two-hour show that combined hits, covers and an uninterrupted chunk of their upcoming Mojo album, Tom Petty and the Heartbreakers once again justified nearly 34 years of popular rock classicism in Oakland on Saturday night. Every new track evoked different early '70s sounds that predate the Heartbreakers' own formation, and most of their enduring FM staples rework styles that stretch back even further. But Petty and cohorts performed with both precision and commitment - a rare combination for a band of vets with a median age nearing 60.