(Reuters) - AstraZeneca's dividend - a key attraction for investors in the drugmaker - will remain safe, despite a change of chief executive and a major strategic review now under way, its chairman said on Tuesday. Leif Johansson, who earlier appointed Roche pharma head Pascal Soriot as AstraZeneca's new CEO from October 1, said the company was fully committed to a progressive dividend policy and also viewed share buybacks as an efficient mechanism for returning cash to shareholders, subject to business needs. ...