Initial support for native accessibility in ARC

components/exo/ax_tree_source_surface.h

Index: components/exo/ax_tree_source_surface.h
diff --git a/components/exo/ax_tree_source_surface.h b/components/exo/ax_tree_source_surface.h
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+++ b/components/exo/ax_tree_source_surface.h
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+// 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 COMPONENTS_EXO_AX_TREE_SOURCE_SURFACE_H_
+#define COMPONENTS_EXO_AX_TREE_SOURCE_SURFACE_H_
+
+#include "base/observer_list.h"
+#include "ui/accessibility/ax_enums.h"
+#include "ui/accessibility/ax_node.h"
+#include "ui/accessibility/ax_node_data.h"
+#include "ui/accessibility/ax_tree_data.h"
+#include "ui/accessibility/ax_tree_source.h"
+
+namespace exo {
+
+// An AXTreeSource that contains nodes without backing objects.
+// As a result, events are fired directly on the tree's nodes. Implementers are
+// responsible for updating the tree's contents before event dispatch to
+// observers.
+class AXTreeSourceSurface
+    : public ui::AXTreeSource<ui::AXNode*, ui::AXNodeData, ui::AXTreeData> {
+ public:
+  AXTreeSourceSurface();
+  ~AXTreeSourceSurface() override;
+
+  class Observer {
+   public:
+    virtual void OnAccessibilityEvent(uint32_t node_id, ui::AXEvent event) = 0;
+  };
+
+  // Called by servers to dispatch events.
+  virtual void NotifyAccessibilityEvent(uint32_t node_id, ui::AXEvent event);
+
+  // Called by containing tree sources to observe events from a serving tree.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+ protected:
+  // Subclasses should initialize the source tree and begin serving events.
+  virtual void Reset() = 0;
+
+ private:
+  base::ObserverList<Observer> observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(AXTreeSourceSurface);
+};
+
+}  // namespace exo
+
+#endif  // COMPONENTS_EXO_AX_TREE_SOURCE_SURFACE_H_