Fix NSURLSession delegate instrumentation for NSProxy delegates #14478

[JesusRojass]

Discussion

Fixes #14478. With Performance instrumentation enabled, NSURLSession delegate callbacks were not delivered when the delegate was an NSProxy (e.g. forwarding to a real delegate). The SDK was instrumenting the proxy instead of the underlying delegate, so optional methods like URLSession:dataTask:didReceiveResponse:completionHandler: were never queried or invoked. This change detects proxy delegates via [delegate isProxy], uses FPRProxyObjectHelper to find the real delegate from the proxy’s ivars, and instruments that object instead.

Testing

Existing Firebase Performance tests pass. Added/updated tests:

• FPRNSURLSessionDelegateProxy test helper and tests that use it to verify all delegate methods (including didReceiveResponse:completionHandler: and didResumeAtOffset:expectedTotalBytes:) are forwarded and instrumented when the session delegate is an NSProxy.
• testDelegateURLSessionDownloadDidReceiveResponseCompletionHandler and testProxyDelegateURLSessionDownloadDidReceiveResponseCompletionHandler for the optional data-task response delegate.
• testDelegateURLSessionDownloadTaskDidResumeAtOffsetExpectedTotalBytes and testProxyDelegateURLSessionDownloadTaskDidResumeAtOffsetExpectedTotalBytes use the delegate’s cancel-and-resume flow; FPRNSURLSessionTestDownloadDelegate now uses a per-instance hasCancelledOnce flag instead of a static dispatch_once_t so both tests run correctly.

API Changes

• No API Changes

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[JesusRojass]

@tejasd @visumickey

Ready for review!!!

[JesusRojass]

/gemini review

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[JesusRojass]

/gemini review

[gemini-code-assist]

Code Review

This pull request addresses an issue where NSURLSession delegate callbacks were not being delivered when the delegate was an NSProxy. The changes introduce a new registerProxy method in FPRObjectInstrumentor and FPRProxyObjectHelper to correctly identify and instrument the real delegate behind the proxy. This ensures that optional delegate methods are properly queried and invoked. The test suite has been updated with new proxy-specific tests to verify the fix.