Remove VirtualSocketServer's dependency on PhysicalSocketServer.

webrtc/base/virtualsocket_unittest.cc

Index: webrtc/base/virtualsocket_unittest.cc
diff --git a/webrtc/base/virtualsocket_unittest.cc b/webrtc/base/virtualsocket_unittest.cc
index 54a52d9eae207b8a93501cfb7bc42970dd72ece1..cab8bb0dc39821514d54ff0dbeb2c257a59bce04 100644
--- a/webrtc/base/virtualsocket_unittest.cc
+++ b/webrtc/base/virtualsocket_unittest.cc
@@ -146,8 +146,7 @@ struct Receiver : public MessageHandler, public sigslot::has_slots<> {
 class VirtualSocketServerTest : public testing::Test {
  public:
   VirtualSocketServerTest()
-      : ss_(nullptr),
-        thread_(&ss_),
+      : thread_(&ss_),
         kIPv4AnyAddress(IPAddress(INADDR_ANY), 0),
         kIPv6AnyAddress(IPAddress(in6addr_any), 0) {}