(Regarding the experimental `React.unstable_Profiler` API and reactjs/rfcs/pull/51.)

PR #13058 changed the behavior of React profiling builds to opt host roots into `ProfileMode` if the React DevTools extension is detected. This was necessary in order to have accurate tree base time measurements for the visual flame graphs.

The Profiler plug-in for DevTools does feature detection to determine if it's enabled by looking at each root and seeing if any of the fibers contain an `actualDuration` attribute,

The problem is that the `actualDuration` attribute will be present on v16.4 fibers, which pre-date PR #13058. As a result, the Profiler UI may enable itself with versions of React that it cannot work correctly with.

Perhaps an easy solution would be to rename one of the `unstable_Profiler`'s fiber attributes prior to the next minor release (e.g. `treeBaseTime` -> `treeBaseDuration`) and change the DevTools Profiler to feature check using this new name instead.
HostPortal,
  Profiler,
  PlaceholderComponent,
} from 'shared/ReactTypeOfWork';
import ReactErrorUtils from 'shared/ReactErrorUtils';
import {
  NoEffect,
  ContentReset,
  Placement,
  Snapshot,
  Update,
} from 'shared/ReactTypeOfSideEffect';
import {commitUpdateQueue} from './ReactUpdateQueue';
import invariant from 'shared/invariant';
import warning from 'shared/warning';
import {Sync} from './ReactFiberExpirationTime';
import {onCommitUnmount} from './ReactFiberDevToolsHook';
import {startPhaseTimer, stopPhaseTimer} from './ReactDebugFiberPerf';
import getComponentName from 'shared/getComponentName';
import {getStackAddendumByWorkInProgressFiber} from 'shared/ReactFiberComponentTreeHook';
import {logCapturedError} from './ReactFiberErrorLogger';
import {
  getPublicInstance,
  supportsMutation,
  supportsPersistence,
  commitMount,
  commitUpdate,
  resetTextContent,
  commitTextUpdate,
  appendChild,