views_bridge_mac: migrate off deprecated NSAccessibility API

This change is pretty simple because there are no uses of these APIs
and only two overrides of deprecated methods:

* BridgedContentView now supports accessibilityChildren directly
* NativeWidgetMacNSWindow now supports accessibilityTitle directly

In informal testing, browser windows and controls seem to still be
navigable using VoiceOver.

Bug: 386671
Change-Id: I46593b863603a4c2155cfd19859ea09401182c1a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1528470
Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641679}

ui/views_bridge_mac/bridged_content_view.mm

@@ -1432,17 +1432,16 @@ ui::TextEditCommand GetTextEditCommandForMenuAction(SEL action) {
     client->EndDrag();
 }
 
-// NSAccessibility informal protocol implementation.
+// NSAccessibility formal protocol implementation:
 
-- (id)accessibilityAttributeValue:(NSString*)attribute {
-  if ([attribute isEqualToString:NSAccessibilityChildrenAttribute]) {
-    if (id accessible = bridge_->host_helper()->GetNativeViewAccessible())
-      return @[ accessible ];
-  }
-
-  return [super accessibilityAttributeValue:attribute];
+- (NSArray*)accessibilityChildren {
+  if (id accessible = bridge_->host_helper()->GetNativeViewAccessible())
+    return @[ accessible ];
+  return [super accessibilityChildren];
 }
 
+// NSAccessibility informal protocol implementation:
+
 - (id)accessibilityHitTest:(NSPoint)point {
   return [bridge_->host_helper()->GetNativeViewAccessible()
       accessibilityHitTest:point];

ui/views_bridge_mac/native_widget_mac_nswindow.mm

@@ -27,7 +27,7 @@
 @interface NativeWidgetMacNSWindow ()
 - (ViewsNSWindowDelegate*)viewsNSWindowDelegate;
 - (BOOL)hasViewsMenuActive;
-- (id)rootAccessibilityObject;
+- (id<NSAccessibility>)rootAccessibilityObject;
 
 // Private API on NSWindow, determines whether the title is drawn on the title
 // bar. The title is still visible in menus, Expose, etc.
@@ -141,9 +141,11 @@
   return hasMenuController;
 }
 
-- (id)rootAccessibilityObject {
-  return bridgeImpl_ ? bridgeImpl_->host_helper()->GetNativeViewAccessible()
-                     : nullptr;
+- (id<NSAccessibility>)rootAccessibilityObject {
+  id<NSAccessibility> obj =
+      bridgeImpl_ ? bridgeImpl_->host_helper()->GetNativeViewAccessible() : nil;
+  DCHECK([obj conformsToProtocol:@protocol(NSAccessibility)]);
+  return obj;
 }
 
 // NSWindow overrides.
@@ -342,18 +344,13 @@
   return bridgeImpl_->host_helper()->GetNativeViewAccessible();
 }
 
-- (id)accessibilityAttributeValue:(NSString*)attribute {
+- (NSString*)accessibilityTitle {
   // Check when NSWindow is asked for its title to provide the title given by
   // the views::RootView (and WidgetDelegate::GetAccessibleWindowTitle()). For
   // all other attributes, use what NSWindow provides by default since diverging
   // from NSWindow's behavior can easily break VoiceOver integration.
-  if (![attribute isEqualToString:NSAccessibilityTitleAttribute])
-    return [super accessibilityAttributeValue:attribute];
-
-  id viewsValue =
-      [[self rootAccessibilityObject] accessibilityAttributeValue:attribute];
-  return viewsValue ? viewsValue
-                    : [super accessibilityAttributeValue:attribute];
+  NSString* viewsValue = self.rootAccessibilityObject.accessibilityTitle;
+  return viewsValue ? viewsValue : [super accessibilityTitle];
 }
 
 @end