Implement caching asynchronous accessibility hit testing.

content/browser/accessibility/browser_accessibility_cocoa.mm

 // 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.
 
 #include <execinfo.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
 
@@ skipping 2835 matching lines @@
 }
 
 // Returns the deepest accessibility child that should not be ignored.
 // It is assumed that the hit test has been narrowed down to this object
 // or one of its children, so this will never return nil unless this
 // object is invalid.
 - (id)accessibilityHitTest:(NSPoint)point {
   if (![self instanceActive])
     return nil;
 
-  BrowserAccessibilityCocoa* hit = self;
-  for (BrowserAccessibilityCocoa* child in [self children]) {
-    if (!child->browserAccessibility_)
-      continue;
-    NSPoint origin = [child origin];
-    NSSize size = [[child size] sizeValue];
-    NSRect rect;
-    rect.origin = origin;
-    rect.size = size;
-    if (NSPointInRect(point, rect)) {
-      hit = child;
-      id childResult = [child accessibilityHitTest:point];
-      if (![childResult accessibilityIsIgnored]) {
-        hit = childResult;
-        break;
-      }
-    }
-  }
-  return NSAccessibilityUnignoredAncestor(hit);
+  BrowserAccessibilityManager* manager = browserAccessibility_->manager();
+  gfx::Point screen_point(point.x, point.y);
+  screen_point += manager->GetViewBounds().OffsetFromOrigin();
+
+  BrowserAccessibility* hit = manager->CachingAsyncHitTest(screen_point);
+  if (!hit)
+    return nil;
+
+  return NSAccessibilityUnignoredAncestor(ToBrowserAccessibilityCocoa(hit));
 }
 
 - (BOOL)isEqual:(id)object {
   if (![object isKindOfClass:[BrowserAccessibilityCocoa class]])
     return NO;
   return ([self hash] == [object hash]);
 }
 
 - (NSUInteger)hash {
   // Potentially called during dealloc.
   if (![self instanceActive])
     return [super hash];
   return browserAccessibility_->GetId();
 }
 
 - (BOOL)accessibilityNotifiesWhenDestroyed {
   // Indicate that BrowserAccessibilityCocoa will post a notification when it's
   // destroyed (see -detach). This allows VoiceOver to do some internal things
   // more efficiently.
   return YES;
 }
 
 @end