Implement caching asynchronous accessibility hit testing.

content/browser/accessibility/browser_accessibility.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_H_
 #define CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 167 matching lines @@
   // returns one past the last character.
   // If the given offset is already at the start of a word, returns the start
   // of the next word if the search is forwards, and the given offset if it is
   // backwards.
   // If the start offset is equal to -1 and the search is in the forwards
   // direction, returns the start boundary of the first word.
   // Start offsets that are not in the range -1 to text length are invalid.
   int GetWordStartBoundary(int start,
                            ui::TextBoundaryDirection direction) const;
 
-  // Returns the deepest descendant that contains the specified point
-  // (in global screen coordinates).
-  BrowserAccessibility* BrowserAccessibilityForPoint(const gfx::Point& point);
+  // This is an approximate hit test that only uses the information in
+  // the browser process to compute the correct result. It will not return
+  // correct results in many cases of z-index, overflow, and absolute
+  // positioning, so BrowserAccessibilityManager::CachingAsyncHitTest
+  // should be used instead, which falls back on calling ApproximateHitTest
+  // automatically.
+  BrowserAccessibility* ApproximateHitTest(const gfx::Point& screen_point);
 
   // Marks this object for deletion, releases our reference to it, and
   // nulls out the pointer to the underlying AXNode.  May not delete
   // the object immediately due to reference counting.
   //
   // Reference counting is used on some platforms because the
   // operating system may hold onto a reference to a BrowserAccessibility
   // object even after we're through with it. When a BrowserAccessibility
   // has had Destroy() called but its reference count is not yet zero,
   // instance_active() returns false and queries on this object return failure.
@@ skipping 176 matching lines @@
   // page coordinates (when |frameOnly| is false), or in frame coordinates
   // (when |frameOnly| is true).
   gfx::Rect RelativeToAbsoluteBounds(gfx::RectF bounds, bool frame_only) const;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserAccessibility);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_H_