First step to move common accessibility code out of content.

ui/accessibility/ax_node.h

Index: ui/accessibility/ax_node.h
diff --git a/ui/accessibility/ax_node.h b/ui/accessibility/ax_node.h
new file mode 100644
index 0000000000000000000000000000000000000000..49e2aa6ccde49148a27430710381ff9c499a5dfc
--- /dev/null
+++ b/ui/accessibility/ax_node.h
@@ -0,0 +1,61 @@
+// Copyright (c) 2013 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_NODE_H_
+#define UI_ACCESSIBILITY_AX_NODE_H_
+
+#include "ui/accessibility/ax_node_data.h"
+
+namespace ui {
+
+// One node in an AXTree.
+class UI_EXPORT AXNode {
+ public:
+  AXNode();
+  virtual ~AXNode();
+
+  // Accessors.
+  int32 id() const { return data_.id; }
+  AXNode* parent() const { return parent_; }
+  int child_count() const { return static_cast<int>(children_.size()); }
+  const AXNodeData& data() const { return data_; }
+  const std::vector<AXNode*>& children() const { return children_; }
+
+  // Get the child at the given index.
+  AXNode* ChildAtIndex(int index) const { return children_[index]; }
+
+  // Initialize the node. This sets up its place in the tree but does
+  // not set its data yet. After initialization, only index_in_parent
+  // is allowed to change, the others are guaranteed to never change.
+  virtual void Init(AXNode* parent, int32 id, int32 index_in_parent);

[David Tseng, 2013/11/15 18:05:31]

Where does this id come from? Id is part of the AXNodeData structure right?

IMO, would be better to just use SetData and eliminate Init.

[dmazzoni, 2013/11/18 08:09:25]

The node isn't valid without a parent, id, and index in parent, but it is valid
with empty data. Also, the parent and id aren't allowed to change, so I don't
want a method that implies they can.

How about this, I moved this to the constructor. That should be more clear.
That means we can't inherit from this class for platform-specific classes, but
we were already moving that direction.

+
+  // Set the node's accessibility data. This may be done during initial
+  // initialization or later when the node data changes.
+  virtual void SetData(const AXNodeData& src);
+
+  // Update the index in parent if siblings were inserted or deleted.
+  void UpdateIndexInParent(int index_in_parent);

[David Tseng, 2013/11/15 18:05:31]

Just a setter; call it SetIndexInParent.

[dmazzoni, 2013/11/18 08:09:25]

Done.

+
+  // Swap the internal children vector with |children|. This instance
+  // now owns all of the passed children.
+  virtual void SwapChildren(std::vector<AXNode*>& children);
+
+  // This is called when the AXTree no longer includes this node in the
+  // tree. Reference counting is used on some platforms because the
+  // operating system may hold onto a reference to an AXNode
+  // object even after we're through with it, so this may decrement the
+  // reference count and clear out the object's data.
+  virtual void Destroy();
+
+ private:
+  int index_in_parent_;
+  AXNode* parent_;
+  std::vector<AXNode*> children_;
+  AXNodeData data_;
+};
+
+
+}  // namespace ui
+
+#endif  // UI_ACCESSIBILITY_AX_NODE_H_