Trastuzumab and Trastuzumab-MCC-DM1 Administered Intravenously and GDC-0941 Administered Orally to Patients With HER2-Positive Metastatic Breast Cancer Who Have Progressed on Previous Trastuzumab-Based Therapy

Inclusion Criteria: * Histologically documented locally advanced or metastatic breast cancer that has progressed on at least one trastuzumab-based regimen in the metastatic or locally advanced setting * HER2-positive disease documented by one of the following results using FDA-approved testing methods: FISH-positive, chromogenic in situ hybridization (CISH)-positive, or IHC 3 + by local laboratory assessment * Life expectancy \>= 90 days * Agreement to use an effective form of contraception for the duration of the study Exclusion Criteria: * History of Grade \>= 3 hypersensitivity reaction to trastuzumab, or Grade \>= 1 with the most recent trastuzumab infusion before study entry, or continued requirement for prolonged trastuzumab infusions to prevent hypersensitivity reactions * History of intolerance to trastuzumab and/or adverse events related to trastuzumab that resulted in trastuzumab being permanently discontinued * Prior anti-cancer therapy (e.g., biologic or other targeted therapy, chemotherapy, hormonal therapy) within 2 weeks prior to Day 1 * Prior investigational anti-cancer therapy within 4 weeks prior to Day 1 * Grade \>= 2 peripheral neuropathy * History of Grade \>= 3 hyperglycemia (fasting) * History of Type 1 or Type 2 diabetes requiring daily medication * History of clinically significant cardiac or pulmonary dysfunction * History of malabsorption syndrome or other condition that would interfere with enteral absorption * Clinically significant history of liver disease, including cirrhosis, current alcohol abuse, or current known active infection with HIV, hepatitis B virus, or hepatitis C virus * Any condition requiring anticoagulants, such as warfarin, heparin, or thrombolytic agents * Any condition requiring \> 2 grams of acetaminophen daily * Need for current chronic corticosteroid therapy * Pregnancy, lactation, or breast-feeding * Current severe, uncontrolled systemic disease (e.g., clinically significant cardiovascular, pulmonary, or metabolic disease) * Major surgical procedure or significant traumatic injury within 28 days prior to Day 1, or anticipation of the need for major surgery during the course of study treatment * Symptomatic hypercalcemia requiring continued use of bisphosphonate therapy * Known brain metastases that are untreated, symptomatic, or require therapy to control symptoms