Initial skeleton of Accessibility Object Model Phase 1

third_party/WebKit/Source/modules/accessibility/ElementAccessibleNode.cpp

+// 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.
+
+#include "modules/accessibility/ElementAccessibleNode.h"
+
+#include "core/dom/Document.h"
+#include "core/frame/Settings.h"
+#include "modules/accessibility/AXObject.h"
+#include "modules/accessibility/AXObjectCacheImpl.h"
+#include "modules/accessibility/AccessibleNode.h"
+#include "platform/RuntimeEnabledFeatures.h"
+
+namespace blink {
+
+AccessibleNode* ElementAccessibleNode::accessibleNode(Element& node) {
+  if (!RuntimeEnabledFeatures::accessibilityObjectModelEnabled())
+    return nullptr;
+
+  Settings* settings = node.document().settings();
+  if (settings && !settings->getAccessibilityEnabled())

[aboxhall, 2017/03/16 05:49:34]

Wait, why do we need to do this? Can we decouple creating this object from
switching on accessibility?

[dmazzoni, 2017/03/16 20:43:16]

Hmmm, good point.

Right now the AXObject for the Element owns the AccessibleNode.
That's convenient because it's the one that needs to access it.

Maybe it'd be better for the Element to own it, but it's not clear to me
how we could do that technically without keeping accessibility code more
decoupled. There are two issues:

* We don't want to add another reference to every Element, we'd want to put
  it in RareData - but we want this code to live in modules/ not in core/
* Alternatively, we could keep track of a map from Element to AccessibleNode
  like we do for the rest of AX code, but then we'd need a callback when an
  Element is deleted / removed from the tree, and currently we do that if
  Accessibility is enabled. Do we want another separate callback system just
  for this independently of accessibility being enabled?

This might be a good question for a Blink owner

+    settings->setAccessibilityEnabled(true);
+
+  // Creates an AXObjectCache if needed.
+  AXObjectCacheImpl* cache =
+      static_cast<AXObjectCacheImpl*>(node.document().axObjectCache());
+  if (!cache)
+    return nullptr;
+
+  DCHECK(cache);
+  AXObject* obj = cache->getOrCreate(&node);
+  if (!obj)
+    return nullptr;
+
+  if (!obj->getAccessibleNode())
+    obj->setAccessibleNode(new AccessibleNode(obj));
+  return obj->getAccessibleNode();
+}
+
+}  // namespace blink