Add hack so VoiceOver speaks updates to injected live regions.

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 b5a42ef04e4f5e33acf1cac82cb5b022016b1518..61e90088ac1271f265e69a03fb15ec2ce2dc191e 100644
--- a/content/browser/accessibility/browser_accessibility_cocoa.mm
+++ b/content/browser/accessibility/browser_accessibility_cocoa.mm
@@ -1030,6 +1030,10 @@ NSDictionary* attributeToMethodNameMap = nil;
   return [attributeToMethodNameMap objectForKey:attribute];
 }
 
+- (void)swapChildren:(base::scoped_nsobject<NSMutableArray>*)other {
+  children_.swap(*other);
+}
+
 // Returns the accessibility value for the given attribute.  If the value isn't
 // supported this will return nil.
 - (id)accessibilityAttributeValue:(NSString*)attribute {