mash: Fix ShelfItem mojo struct; add enums and traits.

ash/public/cpp/shelf_types.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_PUBLIC_CPP_SHELF_TYPES_H_
 #define ASH_PUBLIC_CPP_SHELF_TYPES_H_
 
 #include <cstdint>
 
 #include "ash/public/cpp/ash_public_export.h"
@@ skipping 71 matching lines @@
   // An existing inactive window was activated.
   SHELF_ACTION_WINDOW_ACTIVATED,
 
   // The currently active window was minimized.
   SHELF_ACTION_WINDOW_MINIMIZED,
 
   // The app list launcher menu was shown.
   SHELF_ACTION_APP_LIST_SHOWN,
 };
 
-typedef int ShelfID;
-const int kInvalidShelfID = 0;
+typedef int64_t ShelfID;

[James Cook, 2017/03/16 16:48:50]

nit: using ShelfID = int64_t

Also, are there any useful docs you can add for shelf id, like are they
sequential, are they persistent across restarts of chrome, can they be safely
written to disk, etc.?

Also also, is there a particular motivation to make these int64? Just so they
don't get confused with regular int? If you want to prevent int/shelfid
confusion I wonder if making the ID type unsigned would help generate compiler
warnings. I can't remember if we disable those everywhere anymore.

[msw, 2017/03/16 23:15:50]

Done.
 
Added a comment with some answers.
My motivation was to pick a concrete type that would match mojo, which doesn't
handle 32-/64-bit int type size inference from the platform. They are only
non-negative and generally small (# of shelf items), so I changed this to
uint32_t ... I might need to pair them with a client id (similar to mus windows)
later on.

+const int64_t kInvalidShelfID = 0;
 
 // The type of a shelf item.
 enum ShelfItemType {
   // Represents a running app panel.
   TYPE_APP_PANEL,
 
   // Represents a pinned shortcut to an app, the app may be running or not.
   TYPE_PINNED_APP,
 
   // Toggles visiblity of the app list.
@@ skipping 26 matching lines @@
   STATUS_RUNNING,
   // An active shelf item that has focus.
   STATUS_ACTIVE,
   // A shelf item that needs user's attention.
   STATUS_ATTENTION,
 };
 
 }  // namespace ash
 
 #endif  // ASH_PUBLIC_CPP_SHELF_TYPES_H_