[flags] land enableTrustedTypesIntegration (facebook#35816)

## Summary

This flag enables React's integration with the browser [Trusted Types
API](https://developer.mozilla.org/en-US/docs/Web/API/Trusted_Types_API).

The Trusted Types API is a browser security feature that helps prevent
DOM-based XSS attacks. When a site enables Trusted Types enforcement via
`Content-Security-Policy: require-trusted-types-for 'script'`, the
browser requires that values passed to DOM injection sinks (like
`innerHTML`) are typed objects (`TrustedHTML`, `TrustedScript`,
`TrustedScriptURL`) created through developer-defined sanitization
policies, rather than raw strings.

 ### What changed

Previously, React always coerced values to strings (via `'' + value`)
before passing them to DOM APIs like `setAttribute` and `innerHTML`.
This broke Trusted Types because it converted typed objects into plain
strings, which the browser would then reject under Trusted Types
enforcement.

React now passes values directly to DOM APIs without string coercion,
preserving Trusted Types objects so the browser can validate them. This
applies to `dangerouslySetInnerHTML`, all HTML and SVG attributes, and
URL attributes (`href`, `action`, etc).

 ### Before (broken)

Using Trusted Types with something like`dangerouslySetInnerHTML` would
throw:

 ```js
 const sanitizer = trustedTypes.createPolicy('sanitizer', {
   createHTML: (input) => DOMPurify.sanitize(input),
 });

 function Comment({text}) {
   const clean = sanitizer.createHTML(text);
   // clean is a TrustedHTML object, but React would call '' + clean,
   // converting it back to a plain string before setting innerHTML.
   // Under Trusted Types enforcement, the browser rejects the string:
   //
   //   TypeError: Failed to set 'innerHTML' on 'Element':
   //   This document requires 'TrustedHTML' assignment.
   return <div dangerouslySetInnerHTML={{__html: clean}} />;
 }
 ```

### After (works)

React now passes the TrustedHTML object directly to the DOM without
stringifying it:

```js
 const policy = trustedTypes.createPolicy('sanitizer', {
   createHTML: (input) => DOMPurify.sanitize(input),
 });

 function Comment({text}) {
   // TrustedHTML objects are passed directly to innerHTML
   return <div dangerouslySetInnerHTML={{__html: policy.createHTML(text)}} />;
 }

 function UserProfile({bio}) {
   // String attribute values also preserve Trusted Types objects
   return <div data-bio={policy.createHTML(bio)} />;
 }
 ```

 ## Non-breaking change

 - Sites using Trusted Types: React no longer breaks Trusted Types enforcement. TrustedHTML and TrustedScriptURL objects passed through React props are forwarded to the DOM without being stringified.
 - Sites not using Trusted Types: No behavior change. DOM APIs accept both strings and Trusted Types objects, so removing the explicit string coercion is functionally identical.

Author: rickhanlonii

packages/shared/ReactFeatureFlags.js

@@ -208,7 +208,7 @@ export const disableLegacyMode: boolean = true;
 // in open source, but www codebase still relies on it. Need to remove.
 export const disableCommentsAsDOMContainers: boolean = true;
 
-export const enableTrustedTypesIntegration: boolean = false;
+export const enableTrustedTypesIntegration: boolean = true;
 
 // Prevent the value and checked attributes from syncing with their related
 // DOM properties

packages/shared/forks/ReactFeatureFlags.native-fb.js

@@ -62,7 +62,7 @@ export const enableSuspenseAvoidThisFallback: boolean = false;
 export const enableSuspenseCallback: boolean = true;
 export const enableTaint: boolean = true;
 export const enableTransitionTracing: boolean = false;
-export const enableTrustedTypesIntegration: boolean = false;
+export const enableTrustedTypesIntegration: boolean = true;
 export const enableUpdaterTracking: boolean = __PROFILE__;
 export const retryLaneExpirationMs = 5000;
 export const syncLaneExpirationMs = 250;

packages/shared/forks/ReactFeatureFlags.native-oss.js

@@ -50,7 +50,7 @@ export const enableSuspenseAvoidThisFallback: boolean = false;
 export const enableSuspenseCallback: boolean = false;
 export const enableTaint: boolean = true;
 export const enableTransitionTracing: boolean = false;
-export const enableTrustedTypesIntegration: boolean = false;
+export const enableTrustedTypesIntegration: boolean = true;
 export const passChildrenWhenCloningPersistedNodes: boolean = false;
 export const retryLaneExpirationMs = 5000;
 export const syncLaneExpirationMs = 250;

packages/shared/forks/ReactFeatureFlags.test-renderer.js

@@ -26,7 +26,7 @@ export const disableInputAttributeSyncing: boolean = false;
 export const enableScopeAPI: boolean = false;
 export const enableCreateEventHandleAPI: boolean = false;
 export const enableSuspenseCallback: boolean = false;
-export const enableTrustedTypesIntegration: boolean = false;
+export const enableTrustedTypesIntegration: boolean = true;
 export const disableTextareaChildren: boolean = false;
 export const enableSuspenseAvoidThisFallback: boolean = false;
 export const enableCPUSuspense: boolean = false;

packages/shared/forks/ReactFeatureFlags.test-renderer.native-fb.js

@@ -47,7 +47,7 @@ export const enableSuspenseAvoidThisFallback = false;
 export const enableSuspenseCallback = false;
 export const enableTaint = true;
 export const enableTransitionTracing = false;
-export const enableTrustedTypesIntegration = false;
+export const enableTrustedTypesIntegration = true;
 export const enableUpdaterTracking = false;
 export const passChildrenWhenCloningPersistedNodes = false;
 export const retryLaneExpirationMs = 5000;

packages/shared/forks/ReactFeatureFlags.test-renderer.www.js

@@ -28,7 +28,7 @@ export const enableCreateEventHandleAPI: boolean = false;
 export const enableSuspenseCallback: boolean = true;
 export const disableLegacyContext: boolean = false;
 export const disableLegacyContextForFunctionComponents: boolean = false;
-export const enableTrustedTypesIntegration: boolean = false;
+export const enableTrustedTypesIntegration: boolean = true;
 export const disableTextareaChildren: boolean = false;
 export const enableSuspenseAvoidThisFallback: boolean = true;
 export const enableCPUSuspense: boolean = false;

packages/shared/forks/ReactFeatureFlags.www-dynamic.js

@@ -36,7 +36,6 @@ export const enableFragmentRefs: boolean = __VARIANT__;
 export const enableFragmentRefsScrollIntoView: boolean = __VARIANT__;
 export const enableFragmentRefsTextNodes: boolean = __VARIANT__;
 export const enableInternalInstanceMap: boolean = __VARIANT__;
-export const enableTrustedTypesIntegration: boolean = __VARIANT__;
 export const enableParallelTransitions: boolean = __VARIANT__;
 
 export const enableEffectEventMutationPhase: boolean = __VARIANT__;

packages/shared/forks/ReactFeatureFlags.www.js

@@ -25,7 +25,6 @@ export const {
   enableObjectFiber,
   enableRetryLaneExpiration,
   enableTransitionTracing,
-  enableTrustedTypesIntegration,
   retryLaneExpirationMs,
   syncLaneExpirationMs,
   transitionLaneExpirationMs,
@@ -45,7 +44,7 @@ export const enableProfilerTimer = __PROFILE__;
 export const enableProfilerCommitHooks = __PROFILE__;
 export const enableProfilerNestedUpdatePhase = __PROFILE__;
 export const enableUpdaterTracking = __PROFILE__;
-
+export const enableTrustedTypesIntegration: boolean = true;
 export const enableSuspenseAvoidThisFallback: boolean = true;
 
 export const enableAsyncDebugInfo: boolean = true;