ICoreWebView2WebResourceRequest get_Content passes back a stream object with invalid pointer to Read method

Description
Our Win32 app uses WebView2 to display some web pages and inspect the GET and POST requests sent while the page is loading etc. In our Invoke function we attempt to read the POST request data, like this:

	HRESULT STDMETHODCALLTYPE
	Invoke (ICoreWebView2* webview, ICoreWebView2WebResourceRequestedEventArgs* args)
	{
		ICoreWebView2WebResourceRequest* req;
		IStream* strm;
		HRESULT hr;

		hr = args->get_Request(&req);
		if (SUCCEEDED(hr)) {
			hr = req->get_Content(&strm);
			if (SUCCEEDED(hr)) {
				char *data = (char *)HeapAlloc(GetProcessHeap(), 0, 32768);
				if (data != NULL) {
					DWORD actcount = 0;
					hr = strm->Read(data, 32768, &actcount);
					if (hr == S_OK || hr == S_FALSE) {
						/* do stuff with data */
					}
					HeapFree(GetProcessHeap(), 0, data);
				}
			}
		}
		return(S_OK);
	}

the code above will in some cases fail when calling strm->Read(...) with the following:

Exception thrown: read access violation.
ISequentialStream::Read[virtual] was 0xFFFFFFFFFFFFFFFF.

OR

Exception thrown: read access violation.
strm->lpVtbl+1->QueryInterface was 0xFFFFFFFFFFFFFFFF.

Version
SDK: Windows 10 SDK 10.0.20348.0
Runtime: Microsoft.Web.WebView2 1.0.1054.31 and 1.0.1150.38
Framework: Win32
OS: Windows Server 2019 (17763.2686)

AB#38652932

Start with the Win32 Invoke example in the issue and reproduce the failure at IStream::Read after ICoreWebView2WebResourceRequest::get_Content. Compare behavior across the listed WebView2 SDK and runtime versions, and inspect whether the returned stream pointer remains valid. Done means identifying a reliable cause and documenting or resolving the invalid pointer behavior.