chromeos: Fix handling of null in NativeDisplayDelegate

ui/display/manager/forwarding_display_delegate.cc

 // Copyright 2017 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 "ui/display/manager/forwarding_display_delegate.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "mojo/public/cpp/bindings/sync_call_restrictions.h"
@@ skipping 57 matching lines @@
                                           const DisplayMode* mode,
                                           const gfx::Point& origin,
                                           const ConfigureCallback& callback) {
   if (!use_delegate_) {
     // Pretend configuration succeeded. When the first OnConfigurationChanged()
     // is received this will run again and actually happen.
     callback.Run(true);
     return;
   }
 
-  delegate_->Configure(snapshot.display_id(), mode->Clone(), origin, callback);
+  base::Optional<std::unique_ptr<DisplayMode>> transport_mode;
+  if (mode)
+    transport_mode = mode->Clone();
+  delegate_->Configure(snapshot.display_id(), std::move(transport_mode), origin,
+                       callback);
 }
 
 void ForwardingDisplayDelegate::CreateFrameBuffer(const gfx::Size& size) {}
 
 void ForwardingDisplayDelegate::GetHDCPState(
     const DisplaySnapshot& snapshot,
     const GetHDCPStateCallback& callback) {
   delegate_->GetHDCPState(snapshot.display_id(), callback);
 }
 
@@ skipping 63 matching lines @@
 
 void ForwardingDisplayDelegate::ForwardDisplays(
     const GetDisplaysCallback& callback) {
   std::vector<DisplaySnapshot*> snapshot_ptrs;
   for (auto& snapshot : snapshots_)
     snapshot_ptrs.push_back(snapshot.get());
   callback.Run(snapshot_ptrs);
 }
 
 }  // namespace display