cc::SurfaceDependencyTracker should not crash when a Display goes away

components/viz/frame_sinks/mojo_frame_sink_manager.h

 // Copyright 2015 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.
 
 #ifndef COMPONENTS_VIZ_FRAME_SINKS_MOJO_FRAME_SINK_MANAGER_H_
 #define COMPONENTS_VIZ_FRAME_SINKS_MOJO_FRAME_SINK_MANAGER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 77 matching lines @@
   void OnClientConnectionLost(const cc::FrameSinkId& frame_sink_id,
                               bool destroy_compositor_frame_sink) override;
   void OnPrivateConnectionLost(const cc::FrameSinkId& frame_sink_id,
                                bool destroy_compositor_frame_sink) override;
 
   // SurfaceManager should be the first object constructed and the last object
   // destroyed in order to ensure that all other objects that depend on it have
   // access to a valid pointer for the entirety of their lifetimes.
   cc::SurfaceManager manager_;
 
+  std::unique_ptr<cc::SurfaceDependencyTracker> dependency_tracker_;
+
   // Provides a cc::Display for CreateRootCompositorFrameSink().
   DisplayProvider* const display_provider_;
 
   std::unordered_map<cc::FrameSinkId,
                      std::unique_ptr<cc::mojom::MojoCompositorFrameSink>,
                      cc::FrameSinkIdHash>
       compositor_frame_sinks_;
 
   base::ThreadChecker thread_checker_;
 
   cc::mojom::FrameSinkManagerClientPtr client_;
   mojo::Binding<cc::mojom::FrameSinkManager> binding_;
 
   DISALLOW_COPY_AND_ASSIGN(MojoFrameSinkManager);
 };
 
 }  // namespace viz
 
 #endif  //  COMPONENTS_VIZ_FRAME_SINKS_MOJO_FRAME_SINK_MANAGER_H_