Add support for retrieving image thumbnails as part of the accessibility tree.

content/renderer/accessibility/blink_ax_tree_source.h

 // Copyright 2014 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_RENDERER_ACCESSIBILITY_BLINK_AX_TREE_SOURCE_H_
 #define CONTENT_RENDERER_ACCESSIBILITY_BLINK_AX_TREE_SOURCE_H_
 
 #include <stdint.h>
 
 #include "content/common/ax_content_node_data.h"
@@ skipping 36 matching lines @@
   void Thaw();
 
   // It may be necessary to call SetRoot if you're using a WebScopedAXContext,
   // because BlinkAXTreeSource can't get the root of the tree from the
   // WebDocument if accessibility isn't enabled globally.
   void SetRoot(blink::WebAXObject root);
 
   // Walks up the ancestor chain to see if this is a descendant of the root.
   bool IsInTree(blink::WebAXObject node) const;
 
+  // Set the id of the node to fetch image data for. Normally the content
+  // of images is not part of the accessibility tree, but one node at a
+  // time can be designated as the image data node, which will send the
+  // contents of the image with each accessibility update until another
+  // node is designated.
+  int image_data_node_id() { return image_data_node_id_; }
+  void set_image_data_node_id(int id) { image_data_node_id_ = id; }
+
+  void set_max_image_data_size(const gfx::Size& size) {
+    max_image_data_size_ = size;
+  }
+
   // Set the id of the node with accessibility focus. The node with
   // accessibility focus will force loading inline text box children,
   // which aren't always loaded by default on all platforms.
   int accessibility_focus_id() { return accessibility_focus_id_; }
   void set_accessibility_focus_id(int id) { accessibility_focus_id_ = id; }
 
   // AXTreeSource implementation.
   bool GetTreeData(AXContentTreeData* tree_data) const override;
   blink::WebAXObject GetRoot() const override;
   blink::WebAXObject GetFromId(int32_t id) const override;
@@ skipping 26 matching lines @@
   }
 
   blink::WebAXObject ComputeRoot() const;
 
   RenderFrameImpl* render_frame_;
 
   // An explicit root to use, otherwise it's taken from the WebDocument.
   blink::WebAXObject explicit_root_;
 
   // The id of the object with accessibility focus.
-  int accessibility_focus_id_;
+  int accessibility_focus_id_ = -1;
+
+  // The id of the object to fetch image data for.
+  int image_data_node_id_ = -1;
+
+  gfx::Size max_image_data_size_;
 
   // These are updated when calling |Freeze|.
-  bool frozen_;
+  bool frozen_ = false;
   blink::WebDocument document_;
   blink::WebAXObject root_;
   blink::WebAXObject focus_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_ACCESSIBILITY_BLINK_AX_TREE_SOURCE_H_