Restrict number of BlimpContents to [0, 1]

blimp/client/core/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/blimp_client_context_impl.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/threading/sequenced_task_runner_handle.h"
@@ skipping 70 matching lines @@
   io_thread_task_runner_->DeleteSoon(FROM_HERE, net_components_.release());
 }
 
 void BlimpClientContextImpl::SetDelegate(BlimpClientContextDelegate* delegate) {
   delegate_ = delegate;
 }
 
 std::unique_ptr<BlimpContents> BlimpClientContextImpl::CreateBlimpContents() {
   std::unique_ptr<BlimpContents> blimp_contents =
       blimp_contents_manager_->CreateBlimpContents();
-  delegate_->AttachBlimpContentsHelpers(blimp_contents.get());
+  if (blimp_contents)
+    delegate_->AttachBlimpContentsHelpers(blimp_contents.get());
   return blimp_contents;
 }
 
 void BlimpClientContextImpl::Connect() {
   // Lazy initialization of IdentitySource.
   if (!identity_source_) {
     identity_source_ = base::MakeUnique<IdentitySource>(
         delegate_,
         base::Bind(&BlimpClientContextImpl::ConnectToAssignmentSource,
                    base::Unretained(this)));
@@ skipping 58 matching lines @@
   navigation_feature_->set_outgoing_message_processor(
       thread_pipe_manager_->RegisterFeature(BlimpMessage::kNavigation,
                                             navigation_feature_.get()));
   tab_control_feature_->set_outgoing_message_processor(
       thread_pipe_manager_->RegisterFeature(BlimpMessage::kTabControl,
                                             tab_control_feature_.get()));
 }
 
 }  // namespace client
 }  // namespace blimp