Revert of CHECK() if Windows non-blocking connect returns 0.

net/socket/tcp_socket_win.cc

Index: net/socket/tcp_socket_win.cc
diff --git a/net/socket/tcp_socket_win.cc b/net/socket/tcp_socket_win.cc
index 7ebac7c4d68dda240b32daf3bdba7749ca4217b2..6d84fd453afac0ff4e0b2ac14af98839acbb7c4f 100644
--- a/net/socket/tcp_socket_win.cc
+++ b/net/socket/tcp_socket_win.cc
@@ -801,25 +801,30 @@
     result = connect(socket_, storage.addr, storage.addr_len);
   }
 
-  // The MSDN page for connect says:
-  //   With a nonblocking socket, the connection attempt cannot be completed
-  //   immediately. In this case, connect will return SOCKET_ERROR, and
-  //   WSAGetLastError will return WSAEWOULDBLOCK.
-  // which implies that for a nonblocking socket, connect never returns 0.
-  // It's not clear what the correct thing to do is if connect()
-  // returns 0. It's not clear whether this ever happens in practice.
-  // This CHECK() is here to verify that it doesn't.
-  // TODO(ricea): If the CHECK() fires in canary or dev, revert this
-  // CL. If it doesn't, reconsider what we want to do here long-term.
-  CHECK(result);
-
-  int os_error = WSAGetLastError();
-  if (os_error != WSAEWOULDBLOCK) {
-    LOG(ERROR) << "connect failed: " << os_error;
-    connect_os_error_ = os_error;
-    int rv = MapConnectError(os_error);
-    CHECK_NE(ERR_IO_PENDING, rv);
-    return rv;
+  if (!result) {
+    // Connected without waiting!
+    //
+    // The MSDN page for connect says:
+    //   With a nonblocking socket, the connection attempt cannot be completed
+    //   immediately. In this case, connect will return SOCKET_ERROR, and
+    //   WSAGetLastError will return WSAEWOULDBLOCK.
+    // which implies that for a nonblocking socket, connect never returns 0.
+    // It's not documented whether the event object will be signaled or not
+    // if connect does return 0.  So the code below is essentially dead code
+    // and we don't know if it's correct.
+    NOTREACHED();
+
+    if (ResetEventIfSignaled(core_->read_overlapped_.hEvent))
+      return OK;
+  } else {
+    int os_error = WSAGetLastError();
+    if (os_error != WSAEWOULDBLOCK) {
+      LOG(ERROR) << "connect failed: " << os_error;
+      connect_os_error_ = os_error;
+      int rv = MapConnectError(os_error);
+      CHECK_NE(ERR_IO_PENDING, rv);
+      return rv;
+    }
   }
 
   // TODO(ricea): Remove ScopedTracker below once crbug.com/436634 is fixed.