Fix the blimp settings crash.

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 130 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);
   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()),
+        base::Bind(&BlimpClientContextDelegate::OnAuthenticationError,
+                   base::Unretained(delegate_)));
+  }
 }
 
 std::unique_ptr<BlimpContents> BlimpClientContextImpl::CreateBlimpContents(
     gfx::NativeWindow window) {
   std::unique_ptr<BlimpContents> blimp_contents =
       blimp_contents_manager_->CreateBlimpContents(window);
   if (blimp_contents)
     delegate_->AttachBlimpContentsHelpers(blimp_contents.get());
   return blimp_contents;
 }
 
 void BlimpClientContextImpl::Connect() {
-  if (!assignment_fetcher_) {
-    assignment_fetcher_ = base::MakeUnique<AssignmentFetcher>(
-        io_thread_task_runner_, file_thread_task_runner_,
-        delegate_->CreateIdentityProvider(), GetAssignerURL(),
-        base::Bind(&BlimpClientContextImpl::OnAssignmentReceived,
-                   weak_factory_.GetWeakPtr()),
-        base::Bind(&BlimpClientContextDelegate::OnAuthenticationError,
-                   base::Unretained(delegate_)));
-  }
+  DCHECK(assignment_fetcher_);
   assignment_fetcher_->Fetch();
 }
 
 void BlimpClientContextImpl::ConnectWithAssignment(
     const Assignment& assignment) {
   io_thread_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&ClientNetworkComponents::ConnectWithAssignment,
                  base::Unretained(net_components_.get()), assignment));
 }
 
 std::unordered_map<std::string, std::string>
 BlimpClientContextImpl::CreateFeedbackData() {
   return CreateBlimpFeedbackData(blimp_contents_manager_.get());
 }
 
 IdentitySource* BlimpClientContextImpl::GetIdentitySource() {
+  DCHECK(assignment_fetcher_);
   return assignment_fetcher_->GetIdentitySource();
 }
 
 ConnectionStatus* BlimpClientContextImpl::GetConnectionStatus() {
   return &connection_status_;
 }
 
 GURL BlimpClientContextImpl::GetAssignerURL() {
   return GURL(kDefaultAssignerUrl);
 }
@@ skipping 69 matching lines @@
     if (result >= 0) {
       delegate_->OnEngineDisconnected(result);
     } else {
       delegate_->OnNetworkDisconnected(result);
     }
   }
 }
 
 }  // namespace client
 }  // namespace blimp