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

cc/surfaces/surface_manager.cc

 // Copyright 2014 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 "cc/surfaces/surface_manager.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <queue>
@@ skipping 47 matching lines @@
   SurfaceReferencesToStringImpl(root_surface_id_, "", &str);
   // Temporary references will have an asterisk in front of them.
   for (auto& map_entry : temporary_references_)
     SurfaceReferencesToStringImpl(map_entry.first, "* ", &str);
 
   return str.str();
 }
 #endif
 
 void SurfaceManager::SetDependencyTracker(
-    std::unique_ptr<SurfaceDependencyTracker> dependency_tracker) {
-  dependency_tracker_ = std::move(dependency_tracker);
+    SurfaceDependencyTracker* dependency_tracker) {
+  dependency_tracker_ = dependency_tracker;
 }
 
 void SurfaceManager::RequestSurfaceResolution(Surface* pending_surface) {
   if (dependency_tracker_)
     dependency_tracker_->RequestSurfaceResolution(pending_surface);
 }
 
+std::unique_ptr<BeginFrameSource>
+SurfaceManager::CreatePrimaryBeginFrameSource() {
+  return framesink_manager_.CreatePrimaryBeginFrameSource();
+}
+
 std::unique_ptr<Surface> SurfaceManager::CreateSurface(
     base::WeakPtr<CompositorFrameSinkSupport> compositor_frame_sink_support,
     const LocalSurfaceId& local_surface_id) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(local_surface_id.is_valid() && compositor_frame_sink_support);
 
   SurfaceId surface_id(compositor_frame_sink_support->frame_sink_id(),
                        local_surface_id);
 
   // If no surface with this SurfaceId exists, simply create the surface and
@@ skipping 456 matching lines @@
     std::vector<SurfaceId> children(iter->second.begin(), iter->second.end());
     std::sort(children.begin(), children.end());
 
     for (const SurfaceId& child_id : children)
       SurfaceReferencesToStringImpl(child_id, indent + "  ", str);
   }
 }
 #endif  // DCHECK_IS_ON()
 
 }  // namespace cc