Motorola Mobility, which was bought by Google Inc for $12.5 billion, will cut 20 percent of its workforce and shut nearly a third of its offices worldwide, Google said on Monday. “These changes are designed to return Motorola’s mobile devices unit to profitability, after it lost money in fourteen of the last sixteen quarters,” Google said in a filing with the U.S. Securities and Exchange Commission. “While lower expenses are likely to lag the immediate negative impact to revenue, Google sees these actions as a key step for Motorola to achieve sustainable profitability.”