content: Always run EnforceMemoryPolicy() callbacks on the same thread.

content/common/host_discardable_shared_memory_manager.h

 // 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.
 
 #ifndef CONTENT_COMMON_HOST_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
 #define CONTENT_COMMON_HOST_DISCARDABLE_SHARED_MEMORY_MANAGER_H_
 
 #include <vector>
 
+#include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/format_macros.h"
 #include "base/memory/discardable_memory_allocator.h"
 #include "base/memory/discardable_shared_memory.h"
 #include "base/memory/memory_pressure_listener.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/shared_memory.h"
 #include "base/memory/weak_ptr.h"
 #include "base/process/process_handle.h"
 #include "base/synchronization/lock.h"
+#include "base/thread_task_runner_handle.h"
 #include "base/trace_event/memory_dump_provider.h"
 #include "content/common/content_export.h"
 
 namespace content {
 typedef int32_t DiscardableSharedMemoryId;
 
 // Implementation of DiscardableMemoryAllocator that allocates and manages
 // discardable memory segments for the browser process and child processes.
 // This class is thread-safe and instances can safely be used on any thread.
 class CONTENT_EXPORT HostDiscardableSharedMemoryManager
@@ skipping 90 matching lines @@
                          scoped_refptr<MemorySegment>> MemorySegmentMap;
   typedef base::hash_map<int, MemorySegmentMap> ProcessMap;
   ProcessMap processes_;
   // Note: The elements in |segments_| are arranged in such a way that they form
   // a heap. The LRU memory segment always first.
   typedef std::vector<scoped_refptr<MemorySegment>> MemorySegmentVector;
   MemorySegmentVector segments_;
   size_t memory_limit_;
   size_t bytes_allocated_;
   scoped_ptr<base::MemoryPressureListener> memory_pressure_listener_;
+  scoped_refptr<base::SingleThreadTaskRunner>
+      enforce_memory_policy_task_runner_;
+  base::Closure enforce_memory_policy_callback_;
   bool enforce_memory_policy_pending_;
   base::WeakPtrFactory<HostDiscardableSharedMemoryManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(HostDiscardableSharedMemoryManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_HOST_DISCARDABLE_SHARED_MEMORY_MANAGER_H_