LONDON (Reuters) -The dollar firmed on Friday as traders await key inflation data after a downward revision to first-quarter U.S. economic growth suggested the Federal Reserve could still be on track to cut interest rates this year. Meanwhile, the euro edged lower ahead of euro zone inflation data due at 0900 GMT, which could firm expectations for an European Central Bank rate cut next week. Investors are awaiting the release of the Fed's preferred measure of inflation, the Personal Consumption Expenditures (PCE) price index, due at 1230 GMT, for further indications on how the central bank might proceed.