fix(browser): Release the XHR virtualError once the request completed - #24277
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`instrumentXHR` captures a `new Error()` per `open()` call so the HttpClient integration can report where a failed request came from. Nothing ever formats that stack in the common case, so V8 keeps the raw frames, and a raw frame keeps its receiver alive. When a request is opened from the `readystatechange` callback of the previous one, the receiver of one of those frames is the previous XMLHttpRequest, so every completed request in the chain stays reachable from the one currently in flight. The error is only needed while the completion handlers run, so drop it right after. Fixes #24249
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Releases the
virtualErrorthatinstrumentXHRcaptures once the request has completed, so chained XHRs stop retaining each other.open()captures anew Error()per request for the HttpClient integration. Nobody reads.stack, so V8 keeps the raw frames, and a raw frame keeps its receiver alive. In other words, every completed request holds a stack frame pointing at the one before it, so they pile up like a linked list.The alternative was to hoist
setRequestHeaderproxy in a module-level function so its handler holds the virtualError, but that only unhooks the error for pages that registeraddEventListener. Pages that setonreadystatechangewill need a different fix, so clearing the error manually fixes it for both.Fixes #24249