Initial support for accessibility actions on ARC.

ui/accessibility/ax_host_delegate.h

Index: ui/accessibility/ax_host_delegate.h
diff --git a/ui/accessibility/ax_host_delegate.h b/ui/accessibility/ax_host_delegate.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 UI_ACCESSIBILITY_AX_HOST_DELEGATE_H_
+#define UI_ACCESSIBILITY_AX_HOST_DELEGATE_H_
+
+#include "ui/accessibility/ax_action_data.h"
+
+namespace ui {
+
+// Classes that host an accessibility tree in the browser process that also wish
+// to become visible to accessibility clients (e.g. for relaying targets to
+// source accessibility trees), can subclass this delegate.
+//
+// Subclasses can use |tree_id| when annotating their |AXNodeData| for clients
+// to respond with the appropriate target node id.
+class AX_EXPORT AXHostDelegate {
+ public:
+  virtual ~AXHostDelegate();
+
+  // Handle an action from an accessibility client.
+  virtual void PerformAction(const ui::AXActionData& data) = 0;
+
+ protected:
+  // A delegate with an automatically assigned tree id.
+  AXHostDelegate();
+
+  // A delegate with an explicit tree id. The caller is responsible for ensuring
+  // the uniqueness of the id.
+  explicit AXHostDelegate(int32_t tree_id);
+
+  // A tree id appropriate for annotating events sent to an accessibility
+  // client.
+  int32_t tree_id() { return tree_id_; }
+
+ private:
+  // Register or unregister this class with |AXTreeIDRegistry|.
+  void UpdateActiveState(bool active);
+
+  int32_t tree_id_;
+};
+
+}  // namespace ui
+
+#endif  // UI_ACCESSIBILITY_AX_HOST_DELEGATE_H_