Function startWorkTimer

code/composition/public/app.js:7793–7805

(fiber)

}

function startWorkTimer(fiber) {
  if (enableUserTimingAPI) {
    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
      return;
    }
    // If we pause, this is the fiber to unwind from.
    currentFiber = fiber;
    if (!beginFiberMark(fiber, null)) {
      return;
    }
    fiber._debugIsCurrentlyTiming = true;
  }
}

function cancelWorkTimer(fiber) {
  if (enableUserTimingAPI) {