Add reusePort argument to ServerSocket.

runtime/bin/socket_win.cc

Index: runtime/bin/socket_win.cc
diff --git a/runtime/bin/socket_win.cc b/runtime/bin/socket_win.cc
index 87a0b30e2f5350a91da3cfdd841f0967243d14ce..c559730e964fd61001133e9062fb60ba003092e3 100644
--- a/runtime/bin/socket_win.cc
+++ b/runtime/bin/socket_win.cc
@@ -337,18 +337,28 @@ AddressList<InterfaceSocketAddress>* Socket::ListInterfaces(
 intptr_t ServerSocket::CreateBindListen(RawAddr addr,
                                         intptr_t port,
                                         intptr_t backlog,
-                                        bool v6_only) {
+                                        bool v6_only,
+                                        bool reuse_port) {
   SOCKET s = socket(addr.ss.ss_family, SOCK_STREAM, IPPROTO_TCP);
   if (s == INVALID_SOCKET) {
     return -1;
   }
 
   BOOL optval = true;
-  int status = setsockopt(s,
-                          SOL_SOCKET,
-                          SO_EXCLUSIVEADDRUSE,
-                          reinterpret_cast<const char*>(&optval),
-                          sizeof(optval));
+  int status;
+  if (reuse_port) {
+    status = setsockopt(s,
+                        SOL_SOCKET,
+                        SO_REUSEADDR,
+                        reinterpret_cast<const char*>(&optval),
+                        sizeof(optval));
+  } else {
+    status = setsockopt(s,
+                        SOL_SOCKET,
+                        SO_EXCLUSIVEADDRUSE,
+                        reinterpret_cast<const char*>(&optval),
+                        sizeof(optval));
+  }
   if (status == SOCKET_ERROR) {
     DWORD rc = WSAGetLastError();
     closesocket(s);