First step to move common accessibility code out of content.

content/common/ax_tree_impl.h

+// 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 CONTENT_COMMON_AX_TREE_IMPL_H_
+#define CONTENT_COMMON_AX_TREE_IMPL_H_
+
+#include "base/containers/hash_tables.h"
+
+#include "content/common/ax_tree_source.h"
+#include "content/common/content_export.h"
+#include "content/public/common/ax_tree.h"
+#include "content/public/common/ax_tree_update.h"
+
+namespace content {
+
+class AXNodeImpl;
+
+// AXTree is a live, managed tree of AXNode objects that can receive

[David Tseng, 2013/11/11 19:27:18]

AXTreeImpl.

[dmazzoni, 2013/11/12 00:03:04]

Done.

+// updates from another AXTreeSource via AXTreeUpdates, and it can be
+// used as a source for sending updates to another client tree.
+// It's designed to be subclassed to implement support for native
+// accessibility APIs on a specific platform.
+class CONTENT_EXPORT AXTreeImpl
+    : public AXTreeSource<AXNode>,
+      public AXTree {
+ public:
+  AXTreeImpl();

[David Tseng, 2013/11/11 19:27:18]

Again, I'm not sure why we need this?

[dmazzoni, 2013/11/12 00:03:04]

The content API can only contain interfaces.

+  explicit AXTreeImpl(const AXTreeUpdate& initial_state);
+  virtual ~AXTreeImpl();
+
+  // AXTreeSource and AXTree.

[David Tseng, 2013/11/11 19:27:18]

nit: ... implementation (or just make separate sections with comment).

[dmazzoni, 2013/11/12 00:03:04]

Done.

+  virtual AXNode* GetRoot() const OVERRIDE;
+  virtual int32 GetRootId() const OVERRIDE;
+  virtual AXNode* GetFromId(int32 id) const OVERRIDE;

[David Tseng, 2013/11/11 19:27:18]

Do the various platforms need to implement these id getters? It seems like it
could be handled easily by the base class(es); in this case, AXTree.

[dmazzoni, 2013/11/12 00:03:04]

This is the base class. Think of AXTree as just the interface.

+  virtual int32 GetId(const AXNode* node) const OVERRIDE;
+  virtual int GetChildCount(const AXNode* node) const OVERRIDE;
+  virtual AXNode* GetChildAtIndex(const AXNode* node, int index)
+      const OVERRIDE;
+  virtual int32 GetParentId(const AXNode* node) const OVERRIDE;
+  virtual void Serialize(const AXNode* node, AXNodeData* out_data) const
+      OVERRIDE;
+
+  // AXTree.

[David Tseng, 2013/11/11 19:27:18]

nit: ... implementation.

[dmazzoni, 2013/11/12 00:03:04]

Done.

+  // Apply an update from another AXTreeSource.
+  virtual bool Unserialize(const AXTreeUpdate& update) OVERRIDE;
+
+  // Called when a node is removed from the tree.
+  void NodeWasDestroyed(AXNodeImpl* node);

[David Tseng, 2013/11/11 19:27:18]

OnNodeDestroyed

[dmazzoni, 2013/11/12 00:03:04]

Done.

+
+ protected:
+  // Subclasses can override this to use a subclass of AXNodeImpl.
+  virtual AXNodeImpl* CreateNode();
+
+  // This is called from within Unserialize(), it returns true on success.
+  // Subclasses can override this to do additional processing.
+  virtual bool UpdateNode(const AXNodeData& src);
+
+  // Subclasses can override this to do special behavior when the root changes.
+  virtual void OnRootChanged();
+
+ private:
+  AXNodeImpl* CreateAndInitializeNode(
+      AXNodeImpl* parent, int32 id, int32 index_in_parent);
+
+  AXNodeImpl* root_;
+  base::hash_map<int32, AXNodeImpl*> id_map_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_AX_TREE_IMPL_H_