Make ART Concurrent if Legacy Mode is disabled (#28662)

Pulling this out of #28657.

This runs react-art in concurrent mode if disableLegacyMode is true.
Effectively this means that the OSS version will be in concurrent mode
and the `.modern.js` version for Meta will be in concurrent mode, once
the flag flips for modern, but the `.classic.js` version for Meta will
be in legacy mode.

Updates flowing in from above flush synchronously so that they commit as
a unit. This also ensures that refs are resolved before the parent life
cycles. setStates deep in the tree will now be batched using "discrete"
priority but should still happen same task.

DiffTrain build for [5fcaa0a](5fcaa0a)

compiled/facebook-www/REVISION

@@ -1 +1 @@
-8cb6a1c0347a69ad4c580c5cf5f28d8be544d6d4
+5fcaa0a832db9573364cb73738e0a3b4cf2d27f2

compiled/facebook-www/ReactART-dev.classic.js

@@ -66,7 +66,7 @@ if (__DEV__) {
  return self;
  }
 
- var ReactVersion = "19.0.0-www-classic-cbebd2c1";
+ var ReactVersion = "19.0.0-www-classic-19a521f0";
 
  var LegacyRoot = 0;
  var ConcurrentRoot = 1;
@@ -31074,6 +31074,8 @@ if (__DEV__) {
  var _proto4 = Surface.prototype;
 
  _proto4.componentDidMount = function componentDidMount() {
+ var _this = this;
+
  var _this$props = this.props,
  height = _this$props.height,
  width = _this$props.width;
@@ -31085,36 +31087,51 @@ if (__DEV__) {
  false,
  false,
  ""
- );
- updateContainer(this.props.children, this._mountNode, this);
+ ); // We synchronously flush updates coming from above so that they commit together
+ // and so that refs resolve before the parent life cycles.
+
+ flushSync(function () {
+ updateContainer(_this.props.children, _this._mountNode, _this);
+ });
  };
 
  _proto4.componentDidUpdate = function componentDidUpdate(
  prevProps,
  prevState
  ) {
+ var _this2 = this;
+
  var props = this.props;
 
  if (
  props.height !== prevProps.height ||
  props.width !== prevProps.width
  ) {
  this._surface.resize(+props.width, +props.height);
- }
+ } // We synchronously flush updates coming from above so that they commit together
+ // and so that refs resolve before the parent life cycles.
 
- updateContainer(this.props.children, this._mountNode, this);
+ flushSync(function () {
+ updateContainer(_this2.props.children, _this2._mountNode, _this2);
+ });
 
  if (this._surface.render) {
  this._surface.render();
  }
  };
 
  _proto4.componentWillUnmount = function componentWillUnmount() {
- updateContainer(null, this._mountNode, this);
+ var _this3 = this;
+
+ // We synchronously flush updates coming from above so that they commit together
+ // and so that refs resolve before the parent life cycles.
+ flushSync(function () {
+ updateContainer(null, _this3._mountNode, _this3);
+ });
  };
 
  _proto4.render = function render() {
- var _this = this;
+ var _this4 = this;
 
  // This is going to be a placeholder because we don't know what it will
  // actually resolve to because ART may render canvas, vml or svg tags here.
@@ -31125,7 +31142,7 @@ if (__DEV__) {
  var Tag = Mode$1.Surface.tagName;
  return /*#__PURE__*/ React.createElement(Tag, {
  ref: function (ref) {
- return (_this._tagRef = ref);
+ return (_this4._tagRef = ref);
  },
  accessKey: props.accessKey,
  className: props.className,
@@ -31144,33 +31161,33 @@ if (__DEV__) {
  _inheritsLoose(Text, _React$Component2);
 
  function Text(props) {
- var _this2;
+ var _this5;
 
- _this2 = _React$Component2.call(this, props) || this; // We allow reading these props. Ideally we could expose the Text node as
+ _this5 = _React$Component2.call(this, props) || this; // We allow reading these props. Ideally we could expose the Text node as
  // ref directly.
 
  ["height", "width", "x", "y"].forEach(function (key) {
- Object.defineProperty(_assertThisInitialized(_this2), key, {
+ Object.defineProperty(_assertThisInitialized(_this5), key, {
  get: function () {
  return this._text ? this._text[key] : undefined;
  }
  });
  });
- return _this2;
+ return _this5;
  }
 
  var _proto5 = Text.prototype;
 
  _proto5.render = function render() {
- var _this3 = this;
+ var _this6 = this;
 
  // This means you can't have children that render into strings...
  var T = TYPES.TEXT;
  return /*#__PURE__*/ React.createElement(
  T,
  _extends({}, this.props, {
  ref: function (t) {
- return (_this3._text = t);
+ return (_this6._text = t);
  }
  }),
  childrenAsString(this.props.children)

compiled/facebook-www/ReactART-dev.modern.js

@@ -66,7 +66,7 @@ if (__DEV__) {
  return self;
  }
 
- var ReactVersion = "19.0.0-www-modern-62398be5";
+ var ReactVersion = "19.0.0-www-modern-55690e70";
 
  var LegacyRoot = 0;
  var ConcurrentRoot = 1;
@@ -30724,6 +30724,8 @@ if (__DEV__) {
  var _proto4 = Surface.prototype;
 
  _proto4.componentDidMount = function componentDidMount() {
+ var _this = this;
+
  var _this$props = this.props,
  height = _this$props.height,
  width = _this$props.width;
@@ -30735,36 +30737,51 @@ if (__DEV__) {
  false,
  false,
  ""
- );
- updateContainer(this.props.children, this._mountNode, this);
+ ); // We synchronously flush updates coming from above so that they commit together
+ // and so that refs resolve before the parent life cycles.
+
+ flushSync(function () {
+ updateContainer(_this.props.children, _this._mountNode, _this);
+ });
  };
 
  _proto4.componentDidUpdate = function componentDidUpdate(
  prevProps,
  prevState
  ) {
+ var _this2 = this;
+
  var props = this.props;
 
  if (
  props.height !== prevProps.height ||
  props.width !== prevProps.width
  ) {
  this._surface.resize(+props.width, +props.height);
- }
+ } // We synchronously flush updates coming from above so that they commit together
+ // and so that refs resolve before the parent life cycles.
 
- updateContainer(this.props.children, this._mountNode, this);
+ flushSync(function () {
+ updateContainer(_this2.props.children, _this2._mountNode, _this2);
+ });
 
  if (this._surface.render) {
  this._surface.render();
  }
  };
 
  _proto4.componentWillUnmount = function componentWillUnmount() {
- updateContainer(null, this._mountNode, this);
+ var _this3 = this;
+
+ // We synchronously flush updates coming from above so that they commit together
+ // and so that refs resolve before the parent life cycles.
+ flushSync(function () {
+ updateContainer(null, _this3._mountNode, _this3);
+ });
  };
 
  _proto4.render = function render() {
- var _this = this;
+ var _this4 = this;
 
  // This is going to be a placeholder because we don't know what it will
  // actually resolve to because ART may render canvas, vml or svg tags here.
@@ -30775,7 +30792,7 @@ if (__DEV__) {
  var Tag = Mode$1.Surface.tagName;
  return /*#__PURE__*/ React.createElement(Tag, {
  ref: function (ref) {
- return (_this._tagRef = ref);
+ return (_this4._tagRef = ref);
  },
  accessKey: props.accessKey,
  className: props.className,
@@ -30794,33 +30811,33 @@ if (__DEV__) {
  _inheritsLoose(Text, _React$Component2);
 
  function Text(props) {
- var _this2;
+ var _this5;
 
- _this2 = _React$Component2.call(this, props) || this; // We allow reading these props. Ideally we could expose the Text node as
+ _this5 = _React$Component2.call(this, props) || this; // We allow reading these props. Ideally we could expose the Text node as
  // ref directly.
 
  ["height", "width", "x", "y"].forEach(function (key) {
- Object.defineProperty(_assertThisInitialized(_this2), key, {
+ Object.defineProperty(_assertThisInitialized(_this5), key, {
  get: function () {
  return this._text ? this._text[key] : undefined;
  }
  });
  });
- return _this2;
+ return _this5;
  }
 
  var _proto5 = Text.prototype;
 
  _proto5.render = function render() {
- var _this3 = this;
+ var _this6 = this;
 
  // This means you can't have children that render into strings...
  var T = TYPES.TEXT;
  return /*#__PURE__*/ React.createElement(
  T,
  _extends({}, this.props, {
  ref: function (t) {
- return (_this3._text = t);
+ return (_this6._text = t);
  }
  }),
  childrenAsString(this.props.children)