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

cc/surfaces/surface_dependency_tracker.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 "cc/surfaces/surface_dependency_tracker.h"
 
 #include "cc/surfaces/surface.h"
 #include "cc/surfaces/surface_info.h"
 #include "cc/surfaces/surface_manager.h"
 
@@ skipping 31 matching lines @@
   // Referenced surface IDs that aren't currently known to the surface manager
   // or do not have an active CompsotiorFrame block this frame.
   for (const SurfaceId& surface_id :
        pending_frame.metadata.activation_dependencies) {
     Surface* surface_dependency = surface_manager_->GetSurfaceForId(surface_id);
     if (!surface_dependency || !surface_dependency->HasActiveFrame())
       blocked_surfaces_from_dependency_[surface_id].insert(
           surface->surface_id());
   }
 
-  if (!blocked_surfaces_by_id_.count(surface->surface_id()))
-    blocked_surfaces_by_id_.insert(surface->surface_id());
+  blocked_surfaces_by_id_.insert(surface->surface_id());
 
   if (needs_deadline && !frames_since_deadline_set_)
     frames_since_deadline_set_ = 0;
 }
 
 void SurfaceDependencyTracker::OnSurfaceActivated(Surface* surface) {
   blocked_surfaces_by_id_.erase(surface->surface_id());
   NotifySurfaceIdAvailable(surface->surface_id());
 }
 
@@ skipping 127 matching lines @@
       // A blocked surface may have been garbage collected during dependency
       // resolution.
       DCHECK(!blocked_surfaces_by_id_.count(blocked_surface_by_id));
       continue;
     }
     blocked_surface->NotifySurfaceIdAvailable(surface_id);
   }
 }
 
 }  // namespace cc