[DevTools] Stop setting unused global variables

[everettbu]

Mirror of facebook/react#35532
Original author: eps1lon

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We no longer set the following globals since they're not read by DevTools. It also doesn't look like they had any meaningful values anymore which was hidden by missing Flow coverage.

• __REACT_DEVTOOLS_APPEND_COMPONENT_STACK__
• __REACT_DEVTOOLS_BREAK_ON_CONSOLE_ERRORS__
• __REACT_DEVTOOLS_SHOW_INLINE_WARNINGS_AND_ERRORS__
• __REACT_DEVTOOLS_HIDE_CONSOLE_LOGS_IN_STRICT_MODE__
• __REACT_DEVTOOLS_DISABLE_SECOND_CONSOLE_LOG_DIMMING_IN_STRICT_MODE__

__REACT_DEVTOOLS_COMPONENT_FILTERS__ is still set since it's still in use (although not fully functional in the browser extension which I intend to fix).

[greptile-apps]

Greptile Summary

This PR removes unused global variables from React DevTools that are no longer read by the DevTools system. The PR eliminates 5 global variables that had no meaningful values and were not being used:

• __REACT_DEVTOOLS_APPEND_COMPONENT_STACK__
• __REACT_DEVTOOLS_BREAK_ON_CONSOLE_ERRORS__
• __REACT_DEVTOOLS_SHOW_INLINE_WARNINGS_AND_ERRORS__
• __REACT_DEVTOOLS_HIDE_CONSOLE_LOGS_IN_STRICT_MODE__
• __REACT_DEVTOOLS_DISABLE_SECOND_CONSOLE_LOG_DIMMING_IN_STRICT_MODE__

The PR keeps __REACT_DEVTOOLS_COMPONENT_FILTERS__ as it is still actively used throughout the codebase. Additionally, the PR:

• Adds Flow type annotations to improve type safety in packages/react-devtools-extensions/src/main/index.js
• Removes unused event listeners for editor pane visibility events (extensionEditorPaneShown/extensionEditorPaneHidden)
• Exports additional types (Message, SavedPreferencesParams, FrontendEvents) from the bridge module to support the new type annotations
• Adds missing event type definitions to the Logger

This is a straightforward cleanup that reduces technical debt and improves code maintainability by removing dead code.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• This is a clean refactoring that removes dead code. The removed global variables are confirmed to be unused in the codebase (verified via grep). The PR also improves type safety by adding Flow annotations. The changes are well-scoped and don't introduce any new functionality or modify existing behavior - they only remove unused code and add type definitions.
• No files require special attention

Important Files Changed

Filename	Overview
packages/react-devtools-extensions/src/main/index.js	Added Flow type annotations and removed unused event listeners for editor pane show/hide events
packages/react-devtools-inline/src/backend.js	Removed assignments of 5 unused global variables, keeping only __REACT_DEVTOOLS_COMPONENT_FILTERS__

[everettbu]

Upstream PR was closed or merged. Code is synced via branch mirror.