Sync fork with chromium/7827

[huntie]

Summary

Syncs the react-native-devtools-frontend fork with the upstream chromium/7827 branch (most recent stable from https://chromiumdash.appspot.com/branches).

There were a total of ~171 conflicts. The ~80 translated core/i18n/locales/*.json files were taken from upstream (generated artifacts, no RN strings). The remaining source conflicts were resolved as below.

Notable resolutions

Experiments (ExperimentName refactor)

• Upstream moved ExperimentName from core/root/Runtime.ts into a new core/root/ExperimentNames.ts. We re-export it from Runtime.ts so the fork's pervasive Root.Runtime.ExperimentName.* references keep resolving, add the React Native experiments to ExperimentNames.ts, and register them for tests in upstream's new testing/RuntimeHelpers.ts. RNExperimentName/ConditionName stay in Runtime.ts.

Rollup build (⚠️ build-strategy change)

• Upstream replaced the fork's cross-platform @rollup/wasm-node with native rollup, with platform binaries synced from cipd (infra/3pp/tools/rollup_libs) via a new DEPS entry + sync_rollup_libs gclient hook. Adopted the upstream native-rollup approach (per maintainer decision). gclient sync provides the binaries.

rehydrated_devtools_app entrypoint (⚠️ restored)

• Upstream removed entrypoints/rehydrated_devtools_app/ in favour of its new trace_app. The RN debugger opens rehydrated_devtools_app.html by name, so the entrypoint was restored (kept alongside upstream's trace_app). The rehydrating connection accepts both via isTraceApp() || getPathName().includes('rehydrated_devtools_app').

Content Security Policy

• Kept the fork's permissive single-line CSP with 'unsafe-eval' (required by the React DevTools panels and consumed by the rn_fusebox worker-src injection in generate_html_entrypoint.js), reverting upstream's stricter multi-line CSP — consistent with prior syncs.

Connection layer

• Adopted upstream's Connection→ConnectionTransport / WebSocketConnection→WebSocketTransport / RehydratingConnection→RehydratingConnectionTransport renames and the new TraceObject-based hydration flow, while preserving the fork's richer connectionLostDetails ({reason, code, errorType}) callback used by RemoteDebuggingTerminatedScreen and the hosted-mode WebSocket URL handling.

Removed/renamed upstream APIs (re-applied in RN files)

• UI.XLink / <x-link> removed → <devtools-link> (UI kit); UIUtils.createInlineButton removed → inlined; i18n.getFormatLocalizedString → ui/i18n; SimpleView/VBox options-object constructors; Trace.Handlers.Types.ParsedTrace → Trace.TraceModel.ParsedTrace (handler data now under .data); *.css.js imports are branded CSSInJS strings (dropped .cssText); getRegisteredViewExtensions is now a ViewManager instance method; UserMetrics.panelShownInLocation removed upstream (no callers).

Other necessary changes

• Exported the RNPerfMetrics class (TypeScript 6.0 TS4094 on the re-exported singleton).
• Converted the fork's check-license-header ESLint rule to ESM (the rules dir is now ESM).
• Added missing BUILD.gn deps (ui/components/adorners, ui/components/icon_button, ui/kit) and a dropped Root import in NetworkLogView.ts; converted lantern metric test it() callbacks to function() so this is the Mocha context.
• Dropped the fork's nanoid/serialize-javascript/ws dependency overrides (superseded by upstream's newer tree).
• Exempted the RN components from upstream's new no-lit-render-outside-of-view / no-imperative-dom-api / no-adopted-style-sheets lint rules pending a proper view-function migration.
• Accepted upstream's deletion of UserActionRow.test.ts, application/components/StackTrace.ts, elements/components/LayoutPane.ts, and e2e/issues/client-hint-issues_test.ts (fork changes there were incidental formatting / a disabled test).

Post-merge regression fixes (panel audit)

• Window title no longer updated live — entrypoints/rn_fusebox/rn_fusebox.ts: upstream's new DevToolsContext holds the TargetManager singleton, and MainImpl swaps the global context in during bootstrap. FuseboxAppMetadataObserver/FuseboxFeatureObserver constructed during entrypoint eval therefore bound to an orphaned TargetManager and never observed the ReactNativeApplication model. Construct them inside a registerEarlyInitializationRunnable so they attach to the live TargetManager — and, being registered synchronously, before InspectorMain creates the main target.
• Performance panel crash (Cannot find registered action with ID 'timeline.record-reload') — panels/timeline/TimelinePanel.ts: resolve isNode/isReactNative before constructing the panel and set recordReloadAction = null for React Native, where the reload action is intentionally not registered.
• Protocol Monitor experiment no longer revealed its tab — entrypoints/main/MainImpl.ts: upstream gated Protocol Monitor behind a Chromium-flag registerHostExperiment; restored it as a regular UI-toggleable experiments.register so enabling it shows the panel.
• Duplicate [FB-only] Network banner in the empty-list state — panels/network/NetworkLogView.ts: keep the single persistent banner added in the constructor; drop the duplicate prepended in showRecordingHint.
• Performance landing-page CTA wrapping onto multiple lines — panels/timeline/ReactNativeTimelineLandingPage.ts: re-inline the record-button styling lost when upstream removed UIUtils.createInlineButton, so the button renders inline within the sentence.

Test plan

• Build passes — npm run prebuild && npm run build (gn gen + ninja + tsc) completes cleanly; rn_fusebox.html, rehydrated_devtools_app.html, and inspector.html entrypoints generate, with the expected rn_fusebox CSP ('unsafe-eval' + worker-src 'self' blob:).
• Lint passes — npm run lint -- --fix=false on the changed files reports no problems.

Smoke test on rn_fusebox.html (to complete before merge) — using the plan from #172:

• Console
• Sources
• Performance
• Memory (Heap snapshot, Allocation timeline)
• React Components
• React Profiler

Upstreaming plan

• This commit should be sent as a patch to the upstream devtools-frontend repo.
• This commit is React Native-specific and cannot be upstreamed.