I. To determine the safety and tolerability of GDC-0941 when given in combination with cisplatin in patients with androgen receptor-negative (AR-) triple negative (TN) metastatic breast cancer (MBC): assessment of dose limiting toxicities (DLTs) during the first 4 weeks of treatment (cycle 1); determination of the maximally tolerated dose (MTD) and recommended phase II dose of GDC-0941 given in combination with cisplatin. (Phase IB)