Add mash shelf application id support.

mash/shelf/public/interfaces/shelf.mojom

Index: mash/shelf/public/interfaces/shelf.mojom
diff --git a/mash/shelf/public/interfaces/shelf.mojom b/mash/shelf/public/interfaces/shelf.mojom
index 3e7887b271606d4ad449b5772796f31931ed496b..9b21fb18a216e82a2fda60b0c55c6337dbc45049 100644
--- a/mash/shelf/public/interfaces/shelf.mojom
+++ b/mash/shelf/public/interfaces/shelf.mojom
@@ -16,8 +16,8 @@ interface ShelfController {
   SetAlignment(Alignment alignment);
   SetAutoHideBehavior(AutoHideBehavior auto_hide);
 
-  AddItem(ShelfItem item, associated ShelfItemDelegate delegate);
-  RemoveItem(string id);
+  PinItem(ShelfItem item, associated ShelfItemDelegate delegate);
+  UnpinItem(string app_id);
 };
 
 // ShelfObserver is notified on shelf changes; used to persist profile settings.
@@ -55,11 +55,11 @@ struct ContextMenuItem {
 
 // ShelfItem contains the basic fields needed to pin shortcut items.
 struct ShelfItem {
-  // An id, used to correlate windows and shortcuts (eg. 'exe:chrome').
-  string id;
+  // An app id, used to correlate windows and shortcuts (eg. 'mojo:foo').
+  string app_id;
 
-  // A title, used for tooltips, etc. (eg. 'Chrome').
-  string title;
+  // 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;