Fix delegate check BlimpClientContextImpl::SetDelegate

blimp/client/core/context/blimp_client_context_impl.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "blimp/client/core/context/blimp_client_context_impl.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 140 matching lines @@
 
   UMA_HISTOGRAM_BOOLEAN("Blimp.Supported", true);
 }
 
 BlimpClientContextImpl::~BlimpClientContextImpl() {
   io_thread_task_runner_->DeleteSoon(FROM_HERE, net_components_.release());
   connection_status_.RemoveObserver(this);
 }
 
 void BlimpClientContextImpl::SetDelegate(BlimpClientContextDelegate* delegate) {
-  DCHECK(!delegate_ && delegate);
+  DCHECK(!delegate_ || !delegate);
   delegate_ = delegate;
 
   // TODO(xingliu): Pass the IdentityProvider needed by |assignment_fetcher_|
   // in the constructor, see crbug/661848.
   if (delegate_) {
     assignment_fetcher_ = base::MakeUnique<AssignmentFetcher>(
         io_thread_task_runner_, file_thread_task_runner_,
         delegate_->CreateIdentityProvider(), GetAssignerURL(),
         base::Bind(&BlimpClientContextImpl::OnAssignmentReceived,
                    weak_factory_.GetWeakPtr()),
@@ skipping 115 matching lines @@
     if (result >= 0) {
       delegate_->OnEngineDisconnected(result);
     } else {
       delegate_->OnNetworkDisconnected(result);
     }
   }
 }
 
 }  // namespace client
 }  // namespace blimp