Implement caching asynchronous accessibility hit testing.

content/browser/accessibility/browser_accessibility_manager.h

 // Copyright (c) 2012 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_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_MANAGER_H_
 #define CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_MANAGER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 365 matching lines @@
 
   // Returns the BrowserAccessibilityDelegate from |GetRootManager|, above.
   BrowserAccessibilityDelegate* GetDelegateFromRootManager();
 
   // Returns whether this is the top document.
   bool IsRootTree();
 
   // Get a snapshot of the current tree as an AXTreeUpdate.
   ui::AXTreeUpdate SnapshotAXTreeForTesting();
 
+  // Given a point in screen coordinates, trigger an asynchronous hit test
+  // but return the best possible match instantly.
+  //
+  //
+  BrowserAccessibility* CachingAsyncHitTest(const gfx::Point& screen_point);
+
+  // Called in response to a hover event, caches the result for the next
+  // call to CachingAsyncHitTest().
+  void CacheHitTestResult(BrowserAccessibility* hit_test_result);
+
  protected:
   BrowserAccessibilityManager(
       BrowserAccessibilityDelegate* delegate,
       BrowserAccessibilityFactory* factory);
 
   BrowserAccessibilityManager(
       const ui::AXTreeUpdate& initial_tree,
       BrowserAccessibilityDelegate* delegate,
       BrowserAccessibilityFactory* factory);
 
@@ skipping 50 matching lines @@
   // These are only used by the root BrowserAccessibilityManager of a
   // frame tree. Stores the last focused node and last focused manager so
   // that when focus might have changed we can figure out whether we need
   // to fire a focus event.
   //
   // NOTE: these pointers are not cleared, so they should never be
   // dereferenced, only used for comparison.
   BrowserAccessibility* last_focused_node_;
   BrowserAccessibilityManager* last_focused_manager_;
 
+  // These cache the AX tree ID, node ID, and global screen bounds of the
+  // last object found by an asynchronous hit test. Subsequent hit test
+  // requests that remain within this object's bounds will return the same
+  // object, but will also trigger a new asynchronous hit test request.
+  int last_hover_ax_tree_id_;
+  int last_hover_node_id_;
+  gfx::Rect last_hover_bounds_;
+
   // True if the root's parent is in another accessibility tree and that
   // parent's child is the root. Ensures that the parent node is notified
   // once when this subtree is first connected.
   bool connected_to_parent_tree_node_;
 
   // The global ID of this accessibility tree.
   AXTreeIDRegistry::AXTreeID ax_tree_id_;
 
   // If this tree has a parent tree, this is the cached ID of the parent
   // node within that parent tree. It's computed as needed and cached for
   // speed so that it can be accessed quickly if it hasn't changed.
   int parent_node_id_from_parent_tree_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_MANAGER_H_