more comments + remove 'unchecked'

src/libraries/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpHandler.cs

@@ -963,9 +963,9 @@ private async Task StartRequestAsync(WinHttpRequestState state)
                 // call of the response body data. WINHTTP_OPTION_RECEIVE_TIMEOUT sets a timeout on each
                 // lower layer winsock read.
                 // Timeout.InfiniteTimeSpan will be converted to uint.MaxValue milliseconds (~ 50 days).
-                // The result a of double->uint cast is unspecified and may differ on ARM.
+                // The result a of double->uint cast is unspecified and may differ on ARM, returning 0 instead of uint.MaxValue.
                 // To handle Timeout.InfiniteTimespan correctly, we need to cast to Int32 first.
-                uint optionData = unchecked((uint)(int)_receiveDataTimeout.TotalMilliseconds);
+                uint optionData = (uint)(int)_receiveDataTimeout.TotalMilliseconds;
                 SetWinHttpOption(state.RequestHandle, Interop.WinHttp.WINHTTP_OPTION_RECEIVE_TIMEOUT, ref optionData);
 
                 HttpResponseMessage responseMessage =
@@ -1010,10 +1010,10 @@ private unsafe void SetTcpKeepalive(SafeWinHttpHandle sessionHandle)
                     onoff = 1,
 
                     // Timeout.InfiniteTimeSpan will be converted to uint.MaxValue milliseconds (~ 50 days)
-                    // The result a of double->uint cast is unspecified and may differ on ARM.
+                    // The result a of double->uint cast is unspecified and may differ on ARM, returning 0 instead of uint.MaxValue.
                     // To handle Timeout.InfiniteTimespan correctly, we need to cast to Int32 first.
-                    keepaliveinterval = unchecked((uint)(int)_tcpKeepAliveInterval.TotalMilliseconds),
-                    keepalivetime = unchecked((uint)(int)_tcpKeepAliveTime.TotalMilliseconds)
+                    keepaliveinterval = (uint)(int)_tcpKeepAliveInterval.TotalMilliseconds,
+                    keepalivetime = (uint)(int)_tcpKeepAliveTime.TotalMilliseconds
                 };
 
                 SetWinHttpOption(