[GRC] Coordination Unit Graph Observer

services/resource_coordinator/coordination_unit/coordination_unit_graph_observer.h

Index: services/resource_coordinator/coordination_unit/coordination_unit_graph_observer.h
diff --git a/services/resource_coordinator/coordination_unit/coordination_unit_graph_observer.h b/services/resource_coordinator/coordination_unit/coordination_unit_graph_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..9f33e8d8be0a006197478aa8deb0e6655ad4616f
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+++ b/services/resource_coordinator/coordination_unit/coordination_unit_graph_observer.h
@@ -0,0 +1,85 @@
+// Copyright 2017 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 SERVICES_RESOURCE_COORDINATOR_COORDINATION_UNIT_COORDINATION_UNIT_GRAPH_OBSERVER_H_
+#define SERVICES_RESOURCE_COORDINATOR_COORDINATION_UNIT_COORDINATION_UNIT_GRAPH_OBSERVER_H_
+
+#include <memory>
+#include <unordered_map>
+
+#include "base/macros.h"
+#include "services/resource_coordinator/coordination_unit/coordination_unit_impl.h"
+#include "services/resource_coordinator/public/cpp/coordination_unit_id.h"
+#include "services/resource_coordinator/public/cpp/coordination_unit_types.h"
+#include "services/resource_coordinator/public/interfaces/coordination_unit.mojom.h"
+
+namespace resource_coordinator {
+
+// An observer API for the coordination unit graph maintained by GRC.
+//
+// Observers are instantiated when the resource_coordinator service
+// is created and are destroyed when the resource_coordinator service
+// is destroyed. Therefore observers are guaranteed to be alive before
+// any coordination unit is created and will be alive after any
+// coordination unit is destroyed. Additionally, any
+// Coordination Unit reachable within a callback will always be
+// initialized and valid.
+//
+// To create and install a new observer:
+//   (1) derive from this class
+//   (2) register in CoordinationUnitManager::RegisterObserver
+//       inside of CoordinationUnitManager::CoordinationUnitManager
+class CoordinationUnitGraphObserver {
+ public:
+  CoordinationUnitGraphObserver();
+  virtual ~CoordinationUnitGraphObserver();
+
+  // Determines whether or not the observer should be registered with, and
+  // invoked for, the |coordination_unit|.
+  virtual bool ShouldObserve(const CoordinationUnitImpl* coordination_unit) = 0;
+
+  // Called whenever a CoordinationUnit is created.
+  virtual void OnCoordinationUnitCreated(
+      const CoordinationUnitImpl* coordination_unit) {}
+
+  // Called whenever a new parent-child relationship occurs where the
+  // |coordination_unit| is the parent of |child_coordination_unit|
+  virtual void OnChildAdded(
+      const CoordinationUnitImpl* coordination_unit,
+      const CoordinationUnitImpl* child_coordination_unit) {}
+
+  // Called whenever a new parent-child relationship occurs where the
+  // |coordination_unit| is the child of |parent_coordination_unit|.
+  virtual void OnParentAdded(
+      const CoordinationUnitImpl* coordination_unit,
+      const CoordinationUnitImpl* parent_coordination_unit) {}
+
+  // Called whenever a |property| within the |coordination_unit|'s
+  // internal property store has changed.
+  virtual void OnPropertyChanged(const CoordinationUnitImpl* coordination_unit,
+                                 mojom::PropertyType property) {}
+
+  // Called whenever parent-child relationship ends where the
+  // |coordination_unit| was the parent and the |child_coordination_unit|.
+  virtual void OnChildRemoved(
+      const CoordinationUnitImpl* coordination_unit,
+      const CoordinationUnitImpl* child_coordination_unit) {}
+
+  // Called whenever parent-child relationship ends where the
+  // |coordination_unit| was the child and the |child_coordination_unit|.
+  virtual void OnParentRemoved(
+      const CoordinationUnitImpl* coordination_unit,
+      const CoordinationUnitImpl* parent_coordination_unit) {}
+
+  // Called when the |coordination_unit| is about to be destroyed.
+  virtual void OnCoordinationUnitWillBeDestroyed(
+      const CoordinationUnitImpl* coordination_unit) {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(CoordinationUnitGraphObserver);
+};
+
+}  // namespace resource_coordinator
+
+#endif  // SERVICES_RESOURCE_COORDINATOR_COORDINATION_UNIT_COORDINATION_UNIT_GRAPH_OBSERVER_H_