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diff --git a/gfx/layers/ipc/LayerTreeOwnerTracker.h b/gfx/layers/ipc/LayerTreeOwnerTracker.h
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+++ b/gfx/layers/ipc/LayerTreeOwnerTracker.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_LayerTreeOwnerTracker_h
+#define mozilla_layers_LayerTreeOwnerTracker_h
+
+#include "base/process.h"   // for base::ProcessId
+#include "LayersTypes.h"    // for LayersId
+#include "mozilla/Mutex.h"  // for mozilla::Mutex
+
+#include <functional>
+#include <map>
+
+namespace mozilla {
+
+namespace dom {
+class ContentParent;
+}
+
+namespace layers {
+
+/**
+ * A utility class for tracking which content processes should be allowed
+ * to access which layer trees.
+ *
+ * ProcessId's are used to track which content process can access the layer
+ * tree, and in the case of nested browser's we use the top level content
+ * processes' ProcessId.
+ *
+ * This class is only available in the main process and gpu process. Mappings
+ * are synced from main process to the gpu process. The actual syncing happens
+ * in GPUProcessManager, and so this class should not be used directly.
+ */
+class LayerTreeOwnerTracker final {
+ public:
+  static void Initialize();
+  static void Shutdown();
+  static LayerTreeOwnerTracker* Get();
+
+  /**
+   * Map aLayersId and aProcessId together so that that process
+   * can access that layer tree.
+   */
+  void Map(LayersId aLayersId, base::ProcessId aProcessId);
+
+  /**
+   * Remove an existing mapping.
+   */
+  void Unmap(LayersId aLayersId, base::ProcessId aProcessId);
+
+  /**
+   * Checks whether it is okay for aProcessId to access aLayersId.
+   */
+  bool IsMapped(LayersId aLayersId, base::ProcessId aProcessId);
+
+  void Iterate(
+      const std::function<void(LayersId aLayersId, base::ProcessId aProcessId)>&
+          aCallback);
+
+ private:
+  LayerTreeOwnerTracker();
+
+  mozilla::Mutex mLayerIdsLock;
+  std::map<LayersId, base::ProcessId> mLayerIds;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_LayerTreeOwnerTracker_h