React sync for revisions 6bf5e85...aa94237 (facebook#23320)

Summary:
This sync includes the following changes:
- **[45fc46bfa](facebook/react@45fc46bfa )**: 16.8.1 packages //<Brian Vaughn>//
- **[f2e2637c8](facebook/react@f2e2637c8 )**: Backwards compat fix for ReactCurrentDispatcher on older react versions (facebook#14770) //<Brian Vaughn>//
- **[1107b9673](facebook/react@1107b9673 )**: [TestUtils.act] warn when using TestUtils.act in node (facebook#14768) //<Sunil Pai>//
- **[0975ea327](facebook/react@0975ea327 )**: eslint-plugin-react-hooks v1.0.0 //<Brian Vaughn>//
- **[bc9818f24](facebook/react@bc9818f24 )**: Scheduler.unstable_next (facebook#14756) //<Andrew Clark>//
- **[ce6ecd3fb](facebook/react@ce6ecd3fb )**: Add 16.8.0 changelog and update some READMEs (facebook#14692) //<Dan Abramov>//
- **[008a2ab9c](facebook/react@008a2ab9c )**: 16.8.0 //<Brian Vaughn>//
- **[d1326f466](facebook/react@d1326f466 )**: [TestUtils.act] fix return result checking  (facebook#14758) //<Sunil Pai>//
- **[267ed9814](facebook/react@267ed9814 )**: expose `TestUtils.act()` for batching actions in tests (facebook#14744) //<Sunil Pai>//
- **[fb3f7bfde](facebook/react@fb3f7bfde )**: Avoid importing Scheduler directly (facebook#14757) //<Andrew Clark>//
- **[e602b5291](facebook/react@e602b5291 )**: Use SameValue instead of === to check for dispatchAction equivalence (facebook#14752) //<Jessica Franco>//
- **[e489c3f9c](facebook/react@e489c3f9c )**: Update the version with Hooks proposal in README (facebook#14751) //<SToneX>//
- **[c21c41ecf](facebook/react@c21c41ecf )**: Tweak invalid Hook warning and error (facebook#14747) //<Dan Abramov>//
- **[fec00a869](facebook/react@fec00a869 )**: Typo in comment (facebook#14739) //<Deniz Susman>//
- **[66eb29374](facebook/react@66eb29374 )**: Restrict effect return type to a function or nothing (facebook#14119) //<Andrew Clark>//
- **[51c07912a](facebook/react@51c07912a )**: Warn when second argument is passed to useCallback (facebook#14729) //<Dan Abramov>//
- **[70d407583](facebook/react@70d407583 )**: Move Hook mismatch warning to first mismatch site (facebook#14720) //<Andrew Clark>//
- **[ba6477aa3](facebook/react@ba6477aa3 )**: Improve Reducer Hook's lazy init API (facebook#14723) //<Andrew Clark>//
- **[cb1ff430e](facebook/react@cb1ff430e )**: Phased dispatcher (facebook#14701) //<Andrew Clark>//
- **[9d483dcfd](facebook/react@9d483dcfd )**: Spelling abitrarily -> arbitrarily (facebook#14710) //<Peter Donald>//
- **[e19c9e106](facebook/react@e19c9e106 )**: Fix issue with multiple code branches in hooks linter (facebook#14661) //<Yurick>//
- **[f11a9c1cb](facebook/react@f11a9c1cb )**: State update bug in concurrent mode (facebook#14698) //<Brian Vaughn>//
- **[e679a4b6e](facebook/react@e679a4b6e )**: Fix typo in code comment (facebook#14696) //<Greg Hurrell>//
- **[8bcc88f2e](facebook/react@8bcc88f2e )**: Make all readContext() and Hook-in-a-Hook checks DEV-only (facebook#14677) //<Dan Abramov>//
- **[6cb26774e](facebook/react@6cb26774e )**: Enable hooks! (facebook#14679) //<Brian Vaughn>//
- **[73962c366](facebook/react@73962c366 )**: Revert "Revert "Double-render function components with Hooks in DEV in StrictMode" (facebook#14652)" (facebook#14654) //<Dan Abramov>//
- **[994439228](facebook/react@994439228 )**: Put DEV-only code into DEV blocks (facebook#14673) //<Dan Abramov>//
- **[f0befae65](facebook/react@f0befae65 )**: Tweak context invariant message (facebook#14671) //<Dan Abramov>//
- **[a129259ad](facebook/react@a129259ad )**: Disallow reading context during useMemo etc (facebook#14653) //<Dan Abramov>//
- **[c068d31cc](facebook/react@c068d31cc )**: Add unit tests for concurrent mode event dispatching (facebook#14415) //<Sebastian Markbåge>//
- **[38247cba3](facebook/react@38247cba3 )**: --save is no longer needed (facebook#14302) //<SamCortopassi>//
- **[3f0bcaf0d](facebook/react@3f0bcaf0d )**: Importing React for the first example. (facebook#14346) //<Ramón Chancay Ortega>//
- **[ecd919a2f](facebook/react@ecd919a2f )**: RFC: warn when returning different hooks on subsequent renders (facebook#14585) //<Sunil Pai>//
- **[3fbebb2a0](facebook/react@3fbebb2a0 )**: Revert "Double-render function components with Hooks in DEV in StrictMode" (facebook#14652) //<Dan Abramov>//
- **[5fce6488c](facebook/react@5fce6488c )**: Revert "Disallow reading context during useMemo etc" (facebook#14651) //<Dan Abramov>//
- **[fe2ecd276](facebook/react@fe2ecd276 )**: Add test coverage for readContext() on the server (facebook#14649) //<Dan Abramov>//
- **[8f45a7fdc](facebook/react@8f45a7fdc )**: Warn about incorrect use of useImperativeHandle() (facebook#14647) //<Dan Abramov>//
- **[1fcbd2243](facebook/react@1fcbd2243 )**: Disallow reading context during useMemo etc (facebook#14648) //<Dan Abramov>//
- **[2a084f51a](facebook/react@2a084f51a )**: Warn about refs on lazy function components (facebook#14645) //<Dan Abramov>//
- **[b5a3df6e8](facebook/react@b5a3df6e8 )**: Fix typo (facebook#14560) //<Linchengyi>//
- **[9c146e675](facebook/react@9c146e675 )**: fix typo (facebook#14316) //<liunian>//
- **[baa6d40fc](facebook/react@baa6d40fc )**: Mention forwardRef() in <Fn ref={...} /> errors and warnings (facebook#14644) //<Dan Abramov>//
- **[a1414e894](facebook/react@a1414e894 )**: Double-render function components with Hooks in DEV in StrictMode (facebook#14643) //<Dan Abramov>//
- **[10a7a5b5c](facebook/react@10a7a5b5c )**: Fix synchronous thenable rejection (facebook#14633) //<Dan Abramov>//
- **[a2fa6eb98](facebook/react@a2fa6eb98 )**: Move lazy._result assignment (facebook#14632) //<Dan Abramov>//
- **[9120f6c2d](facebook/react@9120f6c2d )**: Support sync thenables for lazy() (facebook#14626) //<Dan Abramov>//
- **[b66e6e41e](facebook/react@b66e6e41e )**: Add directory details to the package.json of all packages (facebook#14628) //<Grey Baker>//
- **[177fb7635](facebook/react@177fb7635 )**: Warn when second callback is passed to setState/dispatch in Hooks (facebook#14625) //<Dan Abramov>//
- **[d17d0b99c](facebook/react@d17d0b99c )**: Use public context.report interface in eslint rules (facebook#14623) //<Sebastian Silbermann>//
- **[4f332885a](facebook/react@4f332885a )**: Fix shallow renderer set instance state after gDSFP before calling sCU (facebook#14613) //<Yi-Shan, Chen>//
- **[e1cd83e49](facebook/react@e1cd83e49 )**: Throw an error when using hooks inside useMemo/useState/useReducer, or .memo's comparator (facebook#14608) //<Sunil Pai>//
- **[be457ca68](facebook/react@be457ca68 )**: Small tweaks to SSR to match facebook#14594 (facebook#14618) //<Dan Abramov>//
- **[17d70df91](facebook/react@17d70df91 )**: Warn when mixing createRoot() and old APIs (facebook#14615) //<Dan Abramov>//
- **[4feab7fc9](facebook/react@4feab7fc9 )**: Add hooks support to ReactShallowRenderer (facebook#14567) //<Dominic Gannaway>//
- **[1454a8be0](facebook/react@1454a8be0 )**: Don't bother comparing constructor when deps are not provided (facebook#14594) //<Andrew Clark>//
- **[71b64d521](facebook/react@71b64d521 )**: Warn if number of hooks increases (facebook#14591) //<Andrew Clark>//
- **[790c8ef04](facebook/react@790c8ef04 )**: Allow useReducer to bail out of rendering by returning previous state (facebook#14569) //<Andrew Clark>//
- **[7ab8a8e97](facebook/react@7ab8a8e97 )**: Added Flow type to keep hooks dispatchers in-sync (facebook#14599) //<Brian Vaughn>//
- **[4392e3821](facebook/react@4392e3821 )**: useDebugValue should throw if used in a class component (facebook#14601) //<Brian Vaughn>//
- **[153a0b598](facebook/react@153a0b598 )**: Add noop useDebugValue hook to partial/server renderer (facebook#14597) //<Brian Vaughn>//
- **[7ad9806d1](facebook/react@7ad9806d1 )**: Tweak to avoid property read (facebook#14593) //<Brandon Dail>//
- **[0fc154751](facebook/react@0fc154751 )**: Avoid new Set([iterable]) for thenables (facebook#14592) //<Brandon Dail>//
- **[edb1f5956](facebook/react@edb1f5956 )**: Support configurable labels for custom hooks (facebook#14559) //<Brian Vaughn>//
- **[3e15b1c69](facebook/react@3e15b1c69 )**: make a fork for ReactCurrentDispatcher (facebook#14588) //<Sunil Pai>//
- **[0005d1e3f](facebook/react@0005d1e3f )**: Fix typo (facebook#14576) //<Carl Mungazi>//
- **[f290138d3](facebook/react@f290138d3 )**: react-debug-tools accepts currentDispatcher ref as param (facebook#14556) //<Brian Vaughn>//
- **[b4ad8e947](facebook/react@b4ad8e947 )**: rename useImperativeMethods -> useImperativeHandle (facebook#14565) //<Sunil Pai>//
- **[ab03e3d65](facebook/react@ab03e3d65 )**: Inject ReactCurrentDispatcher ref to DevTools (facebook#14550) //<Brian Vaughn>//
- **[19ef0ec11](facebook/react@19ef0ec11 )**: Separate current owner and dispatcher (facebook#14548) //<Brian Vaughn>//
- **[a9b035b0c](facebook/react@a9b035b0c )**: Separate Object.is polyfill (facebook#14334) //<Maksim Markelov>//
- **[547e059f0](facebook/react@547e059f0 )**: Simplify wording of key warning (facebook#14503) //<Sophie Alpert>//
- **[3494ee57e](facebook/react@3494ee57e )**: Update ReactUpdateQueue.js (facebook#14521) //<Carl Mungazi>//
- **[659c13963](facebook/react@659c13963 )**: Update ReactFiberScheduler.js (facebook#14477) //<Carl Mungazi>//
- **[c695b2384](facebook/react@c695b2384 )**: React v16.7.0 //<Andrew Clark>//
- **[1c5aa2f23](facebook/react@1c5aa2f23 )**: Move SchedulerFeatureFlags fork to src directory to fix lint //<Andrew Clark>//
- **[653bc582f](facebook/react@653bc582f )**: Create separate SchedulerFeatureFlags instead of using ReactFeatureFlags (facebook#14455) //<Andrew Clark>//
- **[8bfef0da5](facebook/react@8bfef0da5 )**: Make scheduler debugging feature flag static //<Andrew Clark>//
- **[4a1072194](facebook/react@4a1072194 )**: Memoize promise listeners to prevent exponential growth (facebook#14429) //<Andrew Clark>//
- **[535804f5c](facebook/react@535804f5c )**: Removed Fabric-specific feature flag files and updated Rollup to use the (non-Fabric) React Native flag files. (facebook#14437) //<Brian Vaughn>//
- **[2743fb7b2](facebook/react@2743fb7b2 )**: Enable hooks by default for FB React Native renderer (facebook#14435) //<Brian Vaughn>//
- **[7325ebe4d](facebook/react@7325ebe4d )**: Inject overrideProps() fn to DevTools (facebook#14427) //<Brian Vaughn>//
- **[a22880e5e](facebook/react@a22880e5e )**: Add support for Suspense & lazy() to the react-is package (facebook#14423) //<Pleun Vanderbauwhede>//
- **[947bddd5c](facebook/react@947bddd5c )**: Remove redundant argument of getPlugins function (facebook#14419) //<Heaven>//
- **[8df4d59be](facebook/react@8df4d59be )**: Implement pauseExecution, continueExecution, dumpQueue for Scheduler (facebook#14053) //<Kevin Chavez>//
- **[5bb4ad737](facebook/react@5bb4ad737 )**: Added ErrorBoundary tests for useEffect and useLayoutEffect (facebook#14401) //<Brian Vaughn>//
- **[98eb5ae53](facebook/react@98eb5ae53 )**: TestRenderer toJSON should not expose the Array wrapper Suspense uses for hidden trees (facebook#14392) //<Brian Vaughn>//
- **[39489e767](facebook/react@39489e767 )**: Enable hooks in fabric (facebook#14301) //<Spencer Ahrens>//
- **[1dc108e58](facebook/react@1dc108e58 )**: Tweaked wording for v8 "performance cliff" issue //<Brian Vaughn>//

Release Notes:
[GENERAL] [Changed] - React sync for revisions 6bf5e85...aa94237 (React 16.8.1)

Pull Request resolved: facebook#23320

Differential Revision: D13976467

fbshipit-source-id: 9e11552268883db8672d11cf489d3a5949f498b7

.eslintrc

@@ -12,6 +12,7 @@
     "flowtype",
     "prettier",
     "react",
+    "react-hooks",
     "react-native",
     "jest",
   ],
@@ -240,6 +241,10 @@
     "react/self-closing-comp": 1,
     "react/wrap-multilines": 0,
 
+  // React-Hooks Plugin
+  // The following rules are made available via `eslint-plugin-react-hooks`
+    "react-hooks/rules-of-hooks": "error",
+
   // React-Native Plugin
   // The following rules are made available via `eslint-plugin-react-native`
 

Libraries/Renderer/REVISION

@@ -1 +1 @@
-6bf5e859860938b8cb7153ee928c01ad45656969
+aa9423701e99a194d65a8b835882502902a65a50