Add basic support for launching mash shelf pinned apps.

mash/shelf/public/interfaces/shelf.mojom

 // Copyright 2016 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.
 
 module mash.shelf.mojom;
 
 import "mash/shelf/public/interfaces/shelf_constants.mojom";
 import "skia/public/interfaces/bitmap.mojom";
 
 // TODO(msw): Add support for multiple displays (with unified and multi-shelf).
@@ skipping 12 matching lines @@
 };
 
 // ShelfObserver is notified on shelf changes; used to persist profile settings.
 interface ShelfObserver {
   OnAlignmentChanged(Alignment alignment);
   OnAutoHideBehaviorChanged(AutoHideBehavior auto_hide);
 };
 
 // ShelfItemDelegate handles command execution and observes shelf item changes.
 interface ShelfItemDelegate {
+  // Called when a pinned shelf item is invoked without an open window.
+  LaunchItem();
+
   // Called on invocation of a shelf item's context menu command.
   ExecuteCommand(uint32 command_id, int32 event_flags);
 
   // Called when a shelf item is pinned or unpinned.
   ItemPinned();
   ItemUnpinned();
 
   // Called when a pinned shelf item is reordered.
   // |order| is the index of the item on the shelf.
   ItemReordered(uint32 order);
@@ skipping 19 matching lines @@
 
   // A app title, used for tooltips, etc. (eg. 'Foo Application').
   string app_title;
 
   // An icon image Bitmap, shown on the shelf.
   skia.mojom.Bitmap image;
 
   // Additional context menu items (eg. 'New Incognito Window').
   array<ContextMenuItem>? context_menu_items;
 };