[DevTools Bug]: `sayHelloToBackendManager` continuously and pointlessly polls on every page

Website or app

(all sites)

Repro steps

From any page:

const printMessage = (event) => {console.log(event)};
window.addEventListener('message', printMessage);

Since there isn't a place to actually describe the bug, i'll put it here:
sayHelloToBackendManager is set to poll here until backendInitialized is true: https://github.com/facebook/react/blob/b3003047101b4c7a643788a8faf576f7e370fb45/packages/react-devtools-extensions/src/contentScripts/proxy.js#L17-L23

The polling message has a source react-devtools-content-script: https://github.com/facebook/react/blob/b3003047101b4c7a643788a8faf576f7e370fb45/packages/react-devtools-extensions/src/contentScripts/proxy.js#L41

The switch to set backendInitialized = true checks for the message source react-devtools-bridge: https://github.com/facebook/react/blob/b3003047101b4c7a643788a8faf576f7e370fb45/packages/react-devtools-extensions/src/contentScripts/proxy.js#L65-L66

the react-devtools-bridge sourced message is sent from the backend by whatever invokes this: https://github.com/facebook/react/blob/b3003047101b4c7a643788a8faf576f7e370fb45/packages/react-devtools-extensions/src/contentScripts/backendManager.js#L127

but the handleMessageFromPage function returns if the event.source isn't the window object of the page. Presumably the backend does not have the same window object as the page, or else using postMessage() would be pointless: https://github.com/facebook/react/blob/b3003047101b4c7a643788a8faf576f7e370fb45/packages/react-devtools-extensions/src/contentScripts/proxy.js#L59

The 'react-devtools-bridge' message never flips backendInitialized = true, so the polling never terminates.

This is causing the bitwarden ppl to get a decent amount of heat, and it's actually devtools causing the problem - https://github.com/bitwarden/clients/issues/7575

How often does this bug happen?

Every time

DevTools package (automated)

No response

DevTools version (automated)

No response

Error message (automated)

No response

Error call stack (automated)

No response

Error component stack (automated)

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GitHub query string (automated)

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Start in packages/react-devtools-extensions/src/contentScripts/proxy.js, especially the polling at lines 17-23 and message handling around lines 41 and 59-66. Trace the backend message from packages/react-devtools-extensions/src/contentScripts/backendManager.js around line 127 and reproduce the repeated window messages from any page. Done means the backend initialization message is recognized and polling stops.