Remove VirtualSocketServer's dependency on PhysicalSocketServer.

The only thing the physical socket server was used for was
"Wait"/"WakeUp", but it could be replaced by a simple rtc::Event.

So, removing this dependency makes things less confusing; the fact that
VirtualSocketServer takes a PhysicalSocketServer may lead someone to
think it uses real sockets internally, when it doesn't.

BUG=None

Review-Url: https://codereview.webrtc.org/2883313003
Cr-Commit-Position: refs/heads/master@{#18172}
diff --git a/webrtc/pc/rtcstats_integrationtest.cc b/webrtc/pc/rtcstats_integrationtest.cc
index a2bfb3e..15f0a83 100644
--- a/webrtc/pc/rtcstats_integrationtest.cc
+++ b/webrtc/pc/rtcstats_integrationtest.cc
@@ -18,7 +18,6 @@
 #include "webrtc/api/stats/rtcstatsreport.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/gunit.h"
-#include "webrtc/base/physicalsocketserver.h"
 #include "webrtc/base/refcountedobject.h"
 #include "webrtc/base/scoped_ref_ptr.h"
 #include "webrtc/base/virtualsocketserver.h"
@@ -34,10 +33,7 @@
 class RTCStatsIntegrationTest : public testing::Test {
  public:
   RTCStatsIntegrationTest()
-      : physical_socket_server_(),
-        virtual_socket_server_(&physical_socket_server_),
-        network_thread_(&virtual_socket_server_),
-        worker_thread_() {
+      : network_thread_(&virtual_socket_server_), worker_thread_() {
     RTC_CHECK(network_thread_.Start());
     RTC_CHECK(worker_thread_.Start());
 
@@ -96,10 +92,8 @@
     return stats_obtainer->report();
   }
 
-  // These objects use each other and must be constructed/destroyed in this
-  // order. Relationship:
-  // |physical_socket_server_| <- |virtual_socket_server_| <- |network_thread_|
-  rtc::PhysicalSocketServer physical_socket_server_;
+  // |network_thread_| uses |virtual_socket_server_| so they must be
+  // constructed/destructed in the correct order.
   rtc::VirtualSocketServer virtual_socket_server_;
   rtc::Thread network_thread_;
   rtc::Thread worker_thread_;