Plumb through notification action types and placeholders on Android

ui/message_center/notification.h

Index: ui/message_center/notification.h
diff --git a/ui/message_center/notification.h b/ui/message_center/notification.h
index 93d255e56daa8439201c0348146a3df69e15ee7c..bfca493e164a5d05f2a59cc764dfd2c0d7ad81f8 100644
--- a/ui/message_center/notification.h
+++ b/ui/message_center/notification.h
@@ -10,6 +10,7 @@
 #include <string>
 #include <vector>
 
+#include "base/strings/nullable_string16.h"
 #include "base/strings/string16.h"
 #include "base/time/time.h"
 #include "base/values.h"
@@ -29,11 +30,18 @@ struct MESSAGE_CENTER_EXPORT NotificationItem {
   NotificationItem(const base::string16& title, const base::string16& message);
 };
 
+enum class ButtonType { BUTTON, TEXT };
+
 struct MESSAGE_CENTER_EXPORT ButtonInfo {
   base::string16 title;
   gfx::Image icon;
+  ButtonType type = ButtonType::BUTTON;
+  base::string16 placeholder;
 
-  ButtonInfo(const base::string16& title);
+  explicit ButtonInfo(const base::string16& title);
+  ButtonInfo(const ButtonInfo& other);

[Peter Beverloo, 2016/09/26 16:04:34]

Out of interest, are these still necessary when you change the copy to be a
const reference instead? It'd be great if they're not!

[awdf, 2016/09/27 14:45:27]

Which copy are you talking about, the copy of the notification action on line
449 of
https://codereview.chromium.org/2337963003/diff/120001/chrome/browser/notific...
? Or are you saying I should change the copy constructor signature here?

I thought these methods were required now that there are more than 3 fields in
ButtonInfo so that it needs an out-of-line move operator?

[Peter Beverloo, 2016/09/27 15:28:32]

The one in platform_notification_service_impl.cc indeed.

The rule-of-three (and rule-of-five) are not about number of members, but rather
about which constructors and operators you want to define when the compiler's
asking one of them to be present.

In this case, it may have been the copy that required the copy constructor to
have to be defined at all. If that's the case, we may be able to undo these
modifications, which'd be nice.

On the other hand, it might be that the clang plugin just has a threshold of
three members, after which it starts giving that warning. That'd be confusing in
this instance. Best to try!

[awdf, 2016/09/27 15:36:27]

Oh but I got the clang error before I started caching the notification action in
a variable there, (prior to patch 5) so it must be the threshold-of-3-members
explanation, not a result of copying it there.

+  ~ButtonInfo();
+  ButtonInfo& operator=(const ButtonInfo& other);
 };
 
 class MESSAGE_CENTER_EXPORT RichNotificationData {