MacViews a11y: Sync VoiceOver cursor with keyboard focus.

content/browser/accessibility/browser_accessibility_cocoa.mm

Index: content/browser/accessibility/browser_accessibility_cocoa.mm
diff --git a/content/browser/accessibility/browser_accessibility_cocoa.mm b/content/browser/accessibility/browser_accessibility_cocoa.mm
index a0a8338f3f294ec228f5613173c49785afc1e264..45763cdae9b1e112118f523f7fe405dad50b8948 100644
--- a/content/browser/accessibility/browser_accessibility_cocoa.mm
+++ b/content/browser/accessibility/browser_accessibility_cocoa.mm
@@ -106,11 +106,6 @@ const int kAXResultsLimitNoLimit = -1;
 
 extern "C" {
 
-// See http://openradar.appspot.com/9896491. This SPI has been tested on 10.5,
-// 10.6, and 10.7. It allows accessibility clients to observe events posted on
-// this object.
-void NSAccessibilityUnregisterUniqueIdForUIElement(id element);
-
 // The following are private accessibility APIs required for cursor navigation
 // and text selection. VoiceOver started relying on them in Mac OS X 10.11.
 #if !defined(MAC_OS_X_VERSION_10_11) || \
@@ -610,8 +605,10 @@ NSString* const NSAccessibilityRequiredAttribute = @"AXRequired";
 }
 
 - (void)detach {
-  if (browserAccessibility_)
-    NSAccessibilityUnregisterUniqueIdForUIElement(self);
+  if (!browserAccessibility_)
+    return;
+  NSAccessibilityPostNotification(
+      self, NSAccessibilityUIElementDestroyedNotification);
   browserAccessibility_ = nullptr;
 }
 
@@ -2880,7 +2877,10 @@ NSString* const NSAccessibilityRequiredAttribute = @"AXRequired";
   return browserAccessibility_->GetId();
 }
 
-- (BOOL)accessibilityShouldUseUniqueId {
+- (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;
 }