[Mac] Revert to using the public API to display notification icons

chrome/browser/ui/cocoa/notifications/notification_builder_mac.mm

Index: chrome/browser/ui/cocoa/notifications/notification_builder_mac.mm
diff --git a/chrome/browser/ui/cocoa/notifications/notification_builder_mac.mm b/chrome/browser/ui/cocoa/notifications/notification_builder_mac.mm
index 5b3307afd4116ccc5bf41c381c312c5dc34551c2..e1c8a25813189eae6bc54a6fdd7f4aa34b0e3569 100644
--- a/chrome/browser/ui/cocoa/notifications/notification_builder_mac.mm
+++ b/chrome/browser/ui/cocoa/notifications/notification_builder_mac.mm
@@ -132,16 +132,13 @@ NSString* const kNotificationSettingsButtonTag = @"settingsButton";
 
   // Icon
   if ([notificationData_ objectForKey:kNotificationImage]) {
-    if ([toast respondsToSelector:@selector(_identityImage)]) {
-      if ([[NSImage class] conformsToProtocol:@protocol(NSSecureCoding)]) {
-        NSImage* image = [notificationData_ objectForKey:kNotificationImage];
-        [toast setValue:image forKey:@"_identityImage"];
-      } else {  // NSImage only conforms to NSSecureCoding from 10.10 onwards.
-        base::scoped_nsobject<NSImage> image([[NSImage alloc]
-            initWithData:[notificationData_ objectForKey:kNotificationImage]]);
-        [toast setValue:image forKey:@"_identityImage"];
-      }
-      [toast setValue:@NO forKey:@"_identityImageHasBorder"];
+    if ([[NSImage class] conformsToProtocol:@protocol(NSSecureCoding)]) {
+      NSImage* image = [notificationData_ objectForKey:kNotificationImage];
+      [toast setContentImage:image];
+    } else {  // NSImage only conforms to NSSecureCoding from 10.10 onwards.
+      base::scoped_nsobject<NSImage> image([[NSImage alloc]
+          initWithData:[notificationData_ objectForKey:kNotificationImage]]);
+      [toast setContentImage:image];
     }
   }