Use a lock to deal with concurrent access to the m_evictedBackings

cc/prioritized_resource.h

 // Copyright 2012 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 CC_PRIORITIZED_RESOURCE_H_
 #define CC_PRIORITIZED_RESOURCE_H_
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 104 matching lines @@
         friend class PrioritizedResourceManager;
         PrioritizedResource* m_owner;
         int m_priorityAtLastPriorityUpdate;
         bool m_wasAbovePriorityCutoffAtLastPriorityUpdate;
 
         // Set if this is currently-drawing impl tree.
         bool m_inDrawingImplTree;
 
         bool m_resourceHasBeenDeleted;
 
-        // Set when getEvictedBackings adds this backing to a list, and
-        // un-set unlinkEvictedBackings passes it back in. This must never
-        // be set when already true, and must be false when the backing is
-        // destroyed.
-        bool m_inMainThreadEvictedList;
 #ifndef NDEBUG
         ResourceProvider* m_resourceProvider;
 #endif
         DISALLOW_COPY_AND_ASSIGN(Backing);
     };
 
     PrioritizedResource(PrioritizedResourceManager*, gfx::Size, GLenum format);
 
     bool isAbovePriorityCutoff() { return m_isAbovePriorityCutoff; }
     void setAbovePriorityCutoff(bool isAbovePriorityCutoff) { m_isAbovePriorityCutoff = isAbovePriorityCutoff; }
@@ skipping 14 matching lines @@
 
     Backing* m_backing;
     PrioritizedResourceManager* m_manager;
 
     DISALLOW_COPY_AND_ASSIGN(PrioritizedResource);
 };
 
 }  // namespace cc
 
 #endif  // CC_PRIORITIZED_RESOURCE_H_