Study of GDC-0941 or GDC-0980 With Fulvestrant Versus Fulvestrant in Advanced or Metastatic Breast Cancer in Participants Resistant to Aromatase Inhibitor Therapy

Participants will receive fulvestrant 500 mg as 2 IM injections of 250 mg on Days 1 and 15 of Cycle 1 and on Day 1 of each subsequent cycle, each cycle of 28 days until disease progression, intolerable toxicity, elective withdrawal from the study, study completion or termination.

Participants will receive GDC-0941 260 mg (Part II) or 340 mg (Part I) QD orally from Day 1 or Day 15 of Cycle 1 until disease progression, intolerable toxicity, elective withdrawal from the study, study completion or termination.

Participants will receive GDC-0941 matching placebo QD orally from Day 1 or Day 15 of Cycle 1 until disease progression, intolerable toxicity, elective withdrawal from the study, study completion or termination.

Participants will receive GDC-0980 30 mg (Part I) QD orally from Day 15 of Cycle 1 until disease progression, intolerable toxicity, elective withdrawal from the study, study completion or termination.

Participants will receive GDC-0980 matching placebo QD orally from Day 15 of Cycle 1 until disease progression, intolerable toxicity, elective withdrawal from the study, study completion or termination.